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There has been a lot of confusion and inconsistency regarding defining and discussing the core. This article purposes to clear up some of the confusion and provide ideas for areas in need of future research. The core musculature is a grouping of 29 pairs of muscles that act to statically stabilize the trunk/spine as well as dynamically allow for movement in all planes. Core strength differs from core stability in that strength refers to the ability of a muscle to exert or withstand force, while core stability describes the ability of the body to control the whole range of motion of a joint so there is no major deformity, neurological deficit, or incapacitating pain. The goal of the core musculature is to stabilize/control the trunk/spine throughout full range of motion, preventing abnormal mechanics and subsequent injury. This goal is achieved through coactivation of agonist and antagonistic trunk muscles that stiffen the lumbar spine and therefore increase stability by decreasing the stress/strain place on the inert tissue. Therefore, core exercises are aimed at increasing the muscles ability to stabilize the spine.
The muscles around the trunk and spine have been divided into two categories; local (deep, slow-twitch type 1 fibers, active in endurance) and global (superficial, fast- twitch type 2 fibers, dynamic, active in power activities). The local musculature is composed of deeper trunk muscles, but the primary muscles that are usually considered to act as local stabilizers are the transversus abdominis (TrA) and the multifidus. These muscles have been found to activate prior to limb movement in order to statically stabilize the spine as dynamic movement occurs. The global muscles include the rectus abdominis, lateral fibers of external oblique, psoas major, and erector spinae. These muscles produce more powerful dynamic movements.
The spine is inherently unstable and relies on surrounding muscles for stability, which explains why individuals with low back pain and lumbar instability are often found to have weak local stabilizing musculature (TrA and multifidis).

It has been found that individuals who are shown to have strong global core muscles do not necessarily have equally conditioned endurance of local muscles. Core muscle activation has been measured using ultrasound, magnetic resonance, electromyography, abdominal hollowing (with inflatable biofeedback), and the Sahrmann assessment protocol.

Abdominal hollowing has been proposed as a way to activate the TrA with minimal activation of global muscles, and is defined as the isometric contraction of the abdominal wall without movement of the spine. However, abdominal bracing (coactivation of all abdominal muscles) has now been proposed by some to be more effective in stabilizing the spine because it allows contraction of multiple trunk muscles rather than solely the TrA.

This controversy requires more research, but currently abdominal hollowing is proposed for more static exercises and abdominal bracing is recommended for more dynamic movements with external loads.

The purpose of core strength training is to enhance stability and coordination/ muscle activation of the deep local muscles. A helpful model created by Panjabi
Faries MD, Greenwood M. Core Training: Stabilizing the Confusion. Strength and Conditioning Journal 2007:29;10-25.

categorizes the interaction of the spine into 3 systems: passive (vertebrae, intervertebral discs, zygapophyseal joints, ligaments), active (muscles and tendons), and neural (CNS control over active system). Training of the active system focuses on improving the function of the local system prior to the global system. Exercises used involve little to no movement, low resistance, and focus more on endurance than power.

Exercises that target the global system are incorporated after the local system has been trained and include exercises that involve more dynamic movements through full ranges of motion with higher resistance. Training of the neural system focuses on enhancing timing and coordination of local muscle activation and training the reflex response of stabilizing muscles to decrease reaction time ensuring that local stabilizing muscles are activating prior to the global system and limb movements.

There is little research that has been done regarding optimal progression during core training, so at this point it is recommended to progress according to the FITT (frequency, intensity, time, type) principle. It is very common for individuals to overtrain the global musculature and ignore the local musculature, so it is recommended that emphasis is placed on static training of the local stabilizing musculature throughout the progressing of core training.

It is also recommended to progress toward placing individuals in unstable environments during exercise in order to coactivate local and global musculature and enhance the reflexive coactivation response.
Further research is needed regarding progression of core training programs, functional application, sport specific training, and validation of assessment techniques.
A cervical spine injury can occur in many different athletic situations and the decision to return to play is based on various factors such as the athlete's medical history, physical examination, presence of imaging abnormalities, psychosocial/demographic factors, and level of competition. The purpose of this article was to come to a consensus regarding postinjury management, however due to the uniqueness of each injuries presentation, no consensus was reached.

Transient quadriplegia/paresis is a phenomena that only lasts 10-15 minutes in which injury to the spinal cord causes temporary bilateral burning parasthesia with varying degrees of motor weakness/paresis. Motor and sensory disturbances can vary in amount affected and degree of abnormality.

Transient quadriplegia is associated with developmental cervical stenosis, kyphosis, congenital fusion, cervical instability, intervertebral disc protrusion/ herniation, and vascular and metabolic etiologies. These injuries have been classified by Maroon and Bailes into three stages, with Type 1 being the most severe (permanent spinal cord dysfunction) and Type 3 being the least severe (treatable disorders).

A "stinger" is used to describe a temporary episode of upper extremity dysesthesia with motor weakness that occurs as a result of three different mechanisms: 1) stretch/traction injury to brachial plexus 2) extension of cervical spine resulting in nerve root compression; or 3) direct blow resulting in injury to brachial plexus.

The most common nerve roots affected are C5 and C6.
The Torg ratio was developed to evaluate congenital cervical spine stenosis and is the measure of the anterior-posterior diameter of the spinal canal. It was found that athletes with a Torg ratio less than 0.8 had 3 times greater risk of suffering a stinger.

Torg and Ramsey-Emrhein developed categorizations for cervical posttraumatic conditions as no contraindication, relative contraindication, and absolute contraindication. Relative contraindication to play was given if there was an absence of complete contraindication symptoms, but risk for reinjury was still present.

Absolute contraindications include previously documented episode of neuropraxia with findings of cord abnormalities with MRI imaging (edema, associated ligamentous instability, neurological symptoms lasting more than 36 hrs, and/or multiple episodes of neuropraxia). Specific guidelines for each are outlined in the article.

Cantu et al proposed that an athlete may return to contact/collision sports after 1st episode of transient quadriplegia if there is complete symptom resolution, full ROM, and normal cervical spinal curvature on imaging. However, he recommended relative contraindication in the presence of mild/minimal disc herniation or transient quadriplegia caused by minimal contact.

Overall, a variety of guidelines and principles for return to play after cervical spine injury were provided in this article, but no consensus was made. More research needs to be done regarding these injuries and indications for return to sport.
njuries to the cervical spine constitute uncommon but nonetheless devastating occurrences to those participating in athletic events. These injuries happen primarily to ath- letes involved in the contact sports of football, wrestling, and ice hockey, with football injuries constituting the largest num- ber of cases. The important work of Schneider1 in the mid 1960s, focusing on football-related head and neck injuries, re- sulted in a significant reduction in the incidence of these ac- cidents owing to improvements in equipment, education in proper techniques, offseason conditioning, and rule changes.

Reports of the frequency of serious neck injuries in football players vary, from 1 quadriplegic injury in 7000 participants to 1 in 58 000.2,3

Approximately 40 sport-related cases of vertebral column and 7 of spinal cord injury were reported annually in the Unit- ed States from 1977 to 2004.4,5 A disturbing trend seen in the late 1970s was a drop in the number of serious head injuries in football players but a simultaneous increase in the incidence of cervical injuries, including permanent quadriplegia.

From 1971 to 1975, 259 cervical spine injuries occurred in football players. This correlates to 4.1 per 100000 players, and, of those, 99 cases (1.58 per 100 000 players) resulted in perma- nent quadriplegia.6 Mueller7 noted an increase in cervical spine fatalities to 42 during the 1965-1974 decade.

This was believed to be secondary to improvements in helmet design, which, despite providing protection against head injury, en- couraged the device's use as a battering weapon. Torg et al8 indicated that 85% of all cervical spine injuries from 1971 to 1975 were due to axial loading.

After the no-spearing rule changes in high school and collegiate football were imple- mented in 1976, players were forced to change their tackling echniques, and the incidence of cervical spine injury started to decrease. The decline was dramatic, considering that be- tween 1965 and 1974, 40 fatalities occurred as a result of spinal cord injury, 26 as a result of tackling. Between 1975 and 1984, 14 fatalities occurred from spinal cord injury, 10 as a result of tackling. Between 1985 and 1994, only 5 such fa- talities occurred, all as a result of tackling.7

The purpose of this literature review was to provide athletic trainers with an understanding of the mechanisms, anatomical structures, and complications often associated with sport-re- lated cervical spine injury. Additionally, we present the most current recommendations for management and treatment of these potentially catastrophic injuries to the spine.
Spinal trauma may result in a variety of clinical syndromes, according to the type and severity of the impact and bony displacement as well as the subsequent secondary insults such as hemorrhage, ischemia, and edema. Complete spinal cord injury is a transverse myelopathy with total loss of spinal func- tion below the level of the lesion. This insult is caused by either anatomic disruption of the spinal cord or, more com- monly, hemorrhagic or ischemic damage at the site of injury.

Although the spinal cord usually remains in continuity, a phys- iologic block to impulse transmission results in the complete injury. Complete injury patterns are rarely reversible, although with long-term follow-up, improvement of 1 spinal level may be seen when the initial segmental traumatic spinal cord swell- ing resolves.
Several patterns of incomplete spinal cord injury are com- mon, usually produced on a vascular basis.

The central cord syndrome causes incomplete loss of motor function with a dis- proportionate weakness of the upper extremities as compared with the lower extremities. This condition is thought to be the result of hemorrhagic and ischemic injury to the corticospinal tracts because of their somatotopic arrangement.

Fibers of cer- vical nerves that innervate the upper extremities are arranged more medially than those subserving function to the lower extremities. The originally described central cord syndrome also includes nonspecific sensory loss and bladder and sexual dysfunction.

This injury pattern is also often seen in older patients with vertebral osteophytes and in those with hyper- extension injuries; in the latter, in the absence of fracture, a hyperextension mechanism causes an infolding of the liga- mentum flavum with transient compression of the spinal cord, its blood supply, or both. Due to pre-existing degenerative narrowing within the spinal canal, even a relatively minor fall may produce a neurologic injury in these patients

. The central cord syndrome describes the site of spinal cord injury, but clinical expression is wide ranging and overlaps with other incomplete spinal injury syndromes, especially the Brown-Se- quard syndrome.

Merriam et al9 found in a younger group of patients (mean age of 34.6 years, with half of the patients being less than 30 years old) with central cord syndrome fewer long tract findings, motor deficits limited primarily to the up- per limbs, and a good recovery. Overall, a good prognosis exists for some degree of recovery and often for total func- tional recovery.

The anterior spinal cord syndrome describes an injury that occurs to the anterior two thirds of the spinal cord in the region supplied by the anterior spinal artery.

The neurologic deficit ordinarily consists of a complete loss of all motor function below the level of injury, in addition to loss of sensation con- veyed by the spinothalamic tracts (pain and temperature). Compared with the disproportionate motor deficit seen in cen- tral cord syndrome, deficits in the upper and lower extremities are usually equal, along with sphincteric and sexual dysfunc- tion.

Although the precise mechanism of the pathologic pro- cess is not known, the final common insult is ischemia in the distribution of the anterior spinal artery, which is seen in a variety of spinal column injuries (unlike the strong association of hyperextension injury with central cord syndrome).

Al- though the posterior funiculus of the spinal cord and the dorsal column function are relatively preserved, they are of little im- portance in determining functional outcome due to permanent motor function loss.

The Brown-Sequard syndrome has been classically de- scribed as hemisection of the spinal cord with loss of ipsilat- eral motor function and contralateral spinothalamic (pain and temperature) modalities. This latter finding occurs because of the decussation of the spinothalamic fibers 1 or 2 spinal levels above their entry into the cord, whereas the corticospinal tracts have previously crossed higher in the medullary pyramids and maintain their ipsilateral course to spinal levels of innervation of anterior horn cells.

Although theoretically sound on an an- atomic basis and occasionally seen as a result of penetrating injuries, the Brown-Sequard syndrome usually occurs not in an isolated form but as a combination with other types of incomplete injury. Often a mixture of central cord and Brown- Sequard syndromes is found, in which the patient has some degree of unilateral motor loss and contralateral sensory deficit but with a relatively greater degree of weakness in the upper extremities.

The posterior spinal cord syndrome is an often mentioned but seldom seen clinical entity in which dorsal col- umn function is lost but the corticospinal and spinothalamic tract functions are preserved, believed to be due to selective ischemia in the distribution of the posterior spinal artery.

Many patients have incomplete injuries that are not classi- fiable into any certain pattern. These injuries usually consist of loss of all or nearly all useful motor function below the level of injury, with a sensory loss that does not fit any specific pattern.

This sensory preservation does, however, predict a better recovery than does complete functional loss. The burn- ing hands syndrome is characterized by burning dysesthesias and paresthesias in both hands, commonly seen in athletes who participate in contact sports, especially football and wrestling, with repeated cervical trauma.10

Burning hands syndrome was proposed to be a variant of central cord syndrome with selec- tive injury to the central fibers of the spinothalamic tract that subserve pain and temperature sensation to the upper limbs. Because this injury did not result in permanent loss of either function or pain, it probably occurred as a result of edema or vascular insufficiency. Burning hands syndrome has been known to occur with both fractures and dislocations of the cervical spine and in patients without demonstrable radio- graphic abnormality.

In addition to persons with syndromes caused by blunt trau- ma directed to the spinal column and underlying neural struc- tures, a small group of patients is at risk for neurologic injury resulting from vascular trauma. The carotid and vertebral ar- teries are at risk from direct compression or as a result of traumatic fracture-subluxation. However, a patient with a vas- cular injury may radiographically show only chronic degen- erative changes or have a normal spine.

An injury to any of these large arteries may cause a false channel to appear, with blood coursing distally within the vessel wall and causing a dissection, occlusion, thrombus, embolism, or pseudoaneu- rysm. The carotid arteries are rarely injured in athletic com- petition, but the clinician must keep them in mind whenever signs or symptoms suggest cerebral hemispheric dysfunction (hemiparesis, hemiplegia, hemianesthesia, dysphasia, homon- ymous visual field defects).

A delay in the appearance of the neurologic defect, even up to several days, may occur. Tran- sient ischemic attacks (TIAs) in the anterior or middle cerebral arteries may occur secondary to distal embolization of throm- botic material forming at a site of an intimal tear in the vessel.

Vertebral artery injury may be seen with a fracture or frac- ture-dislocation at or above the C6 vertebra (Figure 1). This may result from direct compression by bony elements, by stretching of the artery by vertical movements, or by an ex- panding traumatic hematoma within the foramen transversar- ium.

Any insult that compromises the structural component of the vessel wall, the tunica intima, or the bony foramen trans- versarium may lead to potentiation of thrombosis embolization or vasospasm, with resultant ascending thrombotic occlusion and hindbrain ischemia. Such an injury to the vertebral artery could be symptomatic immediately after the traumatic insult, with the developing neurologic deficit ranging from gradual and mild to sudden and severe.

The clinical manifestation may be any of a variety of cerebellar or brainstem syndromes. The signs of vertebrobasilar insufficiency or infarction include dys- arthria, emesis, ataxia, visual field deficit, cortical blindness, vertigo, diplopia, long tract deficits, and others. Complete brainstem infarction is rare but can occur.

Computed tomog- raphy (CT) scanning is less likely to show an abnormality in hindbrain ischemic injury than in anterior circulation ischemia, but in either case, if a vascular injury is suspected, emergent angiography (catheter, magnetic resonance [MR] angiography, or CT angiography) must be performed to make the diagnosis
Prompt recognition of any potentially catastrophic injuries is paramount.

Proper management ensures that excessive movement does not exacerbate any initial damage to the spine, thereby reducing the chance of a secondary injury. Initial as- sessment of injury to the cervical spine can be challenging if obvious signs and symptoms are not present. For assessment on the field, it is important to first conduct a primary survey checking for unconsciousness, airway, breathing, and circula- tion to identify any life-threatening injuries.

If no immediate life-threatening conditions are present, then the level of con- sciousness of the individual should be determined and a neu- rologic screening conducted. The evaluation of conscious pa- tients begins with questioning about extremity numbness, painful dysesthesias or paresthesias, weakness, and neck pain.

A limited examination can identify obvious neurologic deficit if the patient is unable to move all or any limbs or has gross weakness, numbness, or significant pain to palpation of the cervical region. If any of these are present on history or ex- amination, or if the athlete is unconscious, transportation should be performed carefully.

In injured athletes with an al- tered level of consciousness, the initial evaluation should check for the possibility of associated head trauma. On-field evaluation should include an examination of level of con- sciousness, cognitive and memory processes, and cranial nerve function, with awareness that significant brain injury is pos- sible.

Every unconscious athlete or injured athlete who complains of numbness, weakness, paralysis, or neck pain should be treated as if he or she has a cervical fracture and, thus, an unstable spine and should be stabilized and transported for further testing and diagnosis.
The athlete should be properly secured to a rigid spine board in such a way that the cervical spine is immobilized and the airway is accessible.11 Several groups have attempted to de- termine the optimal position for the cervical spine to allow the maximum amount of space for the spinal cord. DeLorenzo et al12 determined optimal position of the cervical spine using MR imaging (MRI) and examining the cross-sectional area of the spinal canal versus the spinal cord.

Maximum area was consistently obtained with slight flexion, corresponding to rais- ing the occiput 2 cm. However, these authors did not inves- tigate equipment considerations, and their finding is disputed by Tierney et al,13 who indicated that the most space was present when the occiput was at zero elevation.

Additionally, Tierney et al13 tested a football helmet and shoulder pad con- dition and found no difference in spinal cord space between the zero elevation with or without the equipment. This result is consistent with many other studies and, therefore, leads us to the conclusion that leaving the shoulder pads and helmet on football players is the best plan.

For ice hockey equipment, LaPrade et al14 determined that leaving the helmet and shoulder pads on an ice hockey player was the best choice for maintaining neutral spinal alignment. They found that, with the helmet removed but the shoulder pads remaining, the cervical spine was in a significant amount of lordosis. Therefore, for ice hockey players, the recommen- dation is to leave the helmet on.

This advice is also consistent with the work of Metz et al,15 who determined that the greatest amount of angular displacement occurred when the head rested on the backboard with the shoulder pads still in place.

In addition, helmet removal may create movement that is risky to the integrity of the spinal cord.16,17 Thus, the Inter- Association Task Force for the Appropriate Care of the Spine- Injured Athlete recommended keeping the helmet and shoulder pads on while immobilizing the cervical spine.11
Once the face mask has been removed and the head is still being stabilized by the initial person on the scene, the athlete needs to be transferred to a rigid spine board. This transfer can either be accomplished using a log roll or a 6-person lift (lift-and-slide) technique.

When the athlete is supine, the 6- person lift is recommended, using a scoop stretcher placed under the athlete, who is lifted about 4 to 6 in (10.16 to 15.24 cm) while the spine board is slid underneath.11 The athlete is then lowered down onto the spine board and strapped to it. At least 3 straps should be used to secure the torso, pelvis, and legs.

Mazolewski and Manix19 showed that an added strap across the pelvis significantly reduced the lateral motion of the torso. The head should be secured with towels, blankets, or commercial head immobilizers and then secured to the board with tape. The additional consideration is whether or not to use a cervical collar.

The current recommendation is that a cervical collar should be put on the athlete if that can be done with the pads and helmet still in place. The best combination for head immobilization is a rigid cervical collar and support- ive blocks on either side of the head, with adhesive tape across the forehead.20

Given the circumstances and the equipment, however, it may be impossible to properly fit a cervical collar. Once the athlete is secured to the spine board and strapped down (body first, followed by the head), transport of the ath- lete can begin.
The treatment begins with removal of the athlete from fur- ther participation until the exact nature and injury risk is known. After transport to a definitive care hospital with ade- quate facilities for diagnosis and treatment of such problems, cervical traction with a device such as Gardner-Wells tongs or a halo device may be required for adequate bony reduction and maintenance of alignment in the anatomically neutral po- sition.

This must be done in conjunction with constant radio- graphic assessment and repeated examinations of the patient. At this time, methylprednisolone is administered if it had not been previously administered by the emergency medical ser- vices personnel.

The clinicians must be aware that respiratory and cardiovascular alterations can occur after spinal cord in- jury and must be prepared to treat them effectively as they arise. An intensive care setting is usually the optimal place to care for such injuries in the acute phase. Patients must also be assessed for associated lesions such as head injury, which may have an effect on the clinical course and outcome.

Once the athlete has been initially evaluated and placed in cervical traction to reduce the fracture, a decision must be made as to whether surgical fusion or external orthosis will be used for spinal stabilization.

The current trend in most cases of neck injuries is to attempt nonsurgical fusion by applying a halo vest cervical orthosis. For most patients treated in this manner, adequate bony healing occurs within 12 weeks of halo immobilization.

Surgical treatment continues to be preferred for severe comminuted fractures of the vertebral body, frac- tures of the posterior elements with extreme instability, type II odontoid fractures, and incomplete spinal cord injuries with compromise of the spinal cord as documented on diagnostic studies and in patients who have neurologic deterioration by loss of higher spinal levels of function.

Patients with minor fractures that are stable radiographically as documented by flexion-extension films and who do not have spinal cord injury are allowed to return to their normal daily activities. Athletes with brachial plexus trauma or burning hands may be considered healed when their symptoms resolve and they have no neurologic deficits on examination.

The question of whether to allow an athlete to return to contact sports after a documented or suspected spinal injury has al- ways been an issue. Any athlete who suffers a neurologic in- jury to the spinal cord ordinarily should not be allowed to return. Also, athletes who have had fractures and dislocations of the spine that have required halo brace or surgical stabili- zation probably are best considered not to have adequate strength to withstand subsequent contact sports.

In addition, one must consider the loss of normal movement of the spinal motion segments above and below the area of injury and fu- sion. Some spinal fractures, however, are inherently stable, and when they have occurred without neurologic injury, they do not preclude the athlete from further contact sports. These in- clude isolated laminar or spinous process fractures. Depending on the situation, a healed minor vertebral body fracture, stable according to flexion-extension films, may permit further par- ticipation in contact sports.

On the other hand, strong consideration should be given to disallowing further participation of patients without fractures, instability, or neurologic deficit who suffer repeated injuries with symptoms suggestive of spinal cord involvement (eg, bi- laterality).

An MRI and sometimes somatosensory evoked po- tential testing should be performed in an attempt to demon- strate spinal cord injury, either radiographically or physiologically. These studies may aid in documenting actual neurologic compromise, which would preclude further partic- ipation in contact sports.
Whether an injury represents involvement of the central ner- vous system (spinal cord) or peripheral nerves may be uncer- tain. This situation is best represented by the injury known as ''burners'' or ''stingers'' and is seen most commonly in foot- ball players but also in wrestlers.

This injury results from head and shoulder contact in which the head is laterally flexed to the opposite side with downward traction to the ipsilateral shoulder, causing traction on the upper trunk of the brachial plexus, or by axial loads to the head or shoulders causing injury to the cervical root within its foramen. Typically tran- sient and lasting for up to 15 to 30 minutes, weakness and a searing, lancing pain in the arm may occur.

Residual pain or neurologic deficit corresponding to the upper trunk of the plex- us or cervical nerve root may persist for days or months, and proper management is essential.11

The examiner must consider whether the complaints and any detectable neurologic abnormalities characterize involve- ment of a cervical nerve root, the brachial plexus, or the spinal cord.

Nerve root symptoms include pain radiating into a spe- cific dermatomal pattern, with the possibility of neurologic def- icits related to that dermatomal sensory pattern or to the mus- cle innervated. Plexus involvement is predicted by persistent pain, often in more than one dermatome and sometimes in the entire arm, or by weakness of more than one major muscle group.

Most seriously, one must discern the likelihood of spi- nal cord injury, which is more common if the symptoms are bilateral, occur in the lower extremities, reflect the long tract or include bladder or sexual disturbance. A disturbance of mo- tor or sensory function (or both) on one half of the body may also be of spinal origin.

Electromyography may help in distin- guishing root and plexus injury from spinal cord involvement but ordinarily is not diagnostic until 3 weeks or longer postin- jury. When evidence suggests spinal cord and not root or plex- us injury, a thorough search must be performed to identify a possible occult bony injury or spinal cord contusion. Although rare, acute traumatic rupture of an intervertebral disc or trau- matic hematoma or edema must be considered, and MRI is superior for diagnostic evaluation (Figure 2).

Another group of patients may have congenital spinal canal stenosis, posterior ligamentous compromise, resolved (either medically or surgically) herniated nucleus pulposus (Figure 3), or congenital vertebral body fusion.

These individuals have a heterogeneous assortment of abnormalities, which by them- selves may not require treatment but yet may be associated with a higher risk of injury in contact sports. In general, any patient who has had neck surgery for disc herniation is cleared for further contact sports after postoperative bony fusion is documented. However, the disposition of each patient should be made on an individual basis.
Transient spinal cord injury (TSCI) during athletic compe- tition is one of the most complicated situations the athletic trainer, team physician, paramedic, and neurosurgeon may en- counter.

The initial neurologic signs are often complex, which can make on-field management and subsequent triage difficult. Although usually seen in athletes in traditional contact sports such as football, wrestling, and ice hockey, TSCI may also be seen in other sport activities in which collisions occur, such as basketball, soccer, gymnastics, and baseball.

The occurrence of TSCI is uncommon in athletes, with the incidence estimated to be 7.3 per 10 000 participants in Amer- ican football.21

The condition typically presents with involve- ment of both arms, all 4 extremities, or an ipsilateral arm and leg, consisting of either motor or sensory or combined symp- toms. The most frequent pattern, seen in approximately 80% of cases, is involvement of all 4 extremities with weakness or quadriplegia and combined sensory deficits. The symptoms usually resolve in 15 to 30 minutes but may last for 24 to 48 hours.

Subsequently, the symptoms resolve completely, with pain-free, full range of motion of the cervical spine. Once recovery has occurred, the neurologic examination is typically normal, without residual long tract findings.
The phenomenon of TSCI has been noted for more than a century, with several mechanisms offered to explain the path- ophysiology.

Obersteiner,22 in 1879, described neurologic dys- function termed spinal cord concussion, also subsequently identified in wartime injuries. In 1941, Denny-Brown and Rus- sel23 and later Groat et al24 reported that temporary spinal cord injury resulted from spinal cord neural transmission failure. Penning25 postulated that an extreme movement can occur in high-velocity injuries, resulting in rapid compression of the spinal cord by the posterior-inferior cervical vertebral body and the subjacent spinal lamina.

He termed this the ''pincers effect,'' altering spinal cord impulse transmission via momen- tary impingement without causing a structural failure and, thus, resulting in no lasting radiographic injury.26 Spinal cord concussion has become accepted to mean those instances in which sufficient forces result in temporary inhibition of spinal cord impulse transmission without causing structural damage to the vertebral column or spinal cord.
In our experience and that of others, spinal stenosis is the most common radiographic finding in the athletic population presenting with TSCI (Figures 4 and 5).21,27-29 The sagittal diameter of the cervical canal averages 18.4 mm at C3 and 17.8 mm from the C4 to C7 levels.26,30

Defined as a spinal canal diameter of 14 mm or less, spinal stenosis may be of congenital or acquired forms26,29,31 and asymptomatic.32 Ste- nosis often occurs in athletes secondary to degenerative osteophyte formation, which narrows the canal, probably resulting from repetitive contact sport stresses, and is referred to as ac- quired rather than congenital stenosis. A 3-fold increase in the incidence of peripheral nerve ''burner'' or ''stinger'' injuries, which occur from compression within the foramen, has been associated with spinal stenosis.33,34

Spinal stenosis also has been claimed to result in an increased risk of spinal cord injury due to less available space to accommodate excursions of the spinal cord with elongation, compression, or momentary im- pingement.35,36 Spinal stenosis is associated with a greater chance of neurologic involvement in any person presenting with vertebral column injury.36

The radiographic assessment of the athlete with suspect or proven vertebral column or spinal cord injury includes plain radiographs, MRI, and CT. The vertebral canal-body ratio has been previously proposed as a valid measure of the available space in which the spinal cord resides and moves to escape permanent injury. A canal-body ratio of 0.80 has been con- sidered indicative of spinal stenosis.37

Measurements of the spinal cord among individuals are fairly uniform, but bony anatomy varies significantly among different-sized individuals. Persons with a large body habitus and size are associated with relatively larger vertebral bodies.38

This fact, as well as the ability of MRI to directly image the vertebral column, inter- vertebral discs, spinal canal, and spinal cord, have made MRI (and not bony landmarks) the preferred method for assessing the relative anatomy.

In a previous report39 of 63 athletes with cervical spine injuries in the pre-MRI era, Bailes et al cited 29% who sustained TSCI, with cervical stenosis being the pre- dominant radiographic finding. More recent experience with additional athletes has led to the current emphasis on MRI assessment of cerebrospinal fluid (CSF) signal around the spi- nal cord, termed the functional reserve.

This imaging allows direct visualization of the neural elements, in particular the spinal cord, which improves on the previously known advan- tage of contrast myelography to discern compression and not bony anatomy alone.

The visualization of the CSF signal, its attenuation in areas of stenosis, and changes on dynamic flex- ion-extension MRI studies are paramount for thorough anal- ysis and decision making in this patient population. Patients who do not have a CSF pattern on axial and sagittal MRI views have functional stenosis.27,30
Most athletes who sustain catastrophic spinal cord injury have structural failure of the vertebral column that is not caused by or related to stenosis.4,21,28,30 Catastrophic spinal cord injury in athletes with fracture-dislocation is believed not to result from an athlete's spinal anatomy but instead from the use of techniques that involve making initial contact with the top or crown of the helmet or head. These include being driven into the mat in wrestling, spearing in football, and being knocked into the boards in ice hockey.4,33,40-42

These vertex impacts cause an axial load, most commonly with a flexion component, which leads to structural failure of the vertebral column and spinal cord injury.4,21,28,30 Athletic spinal cord injury does not appear to follow a pattern of repetitive tran- sient injuries culminating in a catastrophic event of vertebral column failure.30

In a survey of 117 football players who sus- tained permanent quadriplegia, none recalled having had a pri- or prodromal experience of motor symptoms; only one (0.9%) had previous sensory symptoms referable to the spinal cord.2

The syndrome of spear tackler's spine is an exception and consists of 4 characteristics: reversal of cervical lordosis; radiographic evidence of previous, healed, minor vertebral body fractures; canal stenosis; and habitual use of spear-tackling techniques.43 In some instances, the factors of spear tackler's syndrome may be corrected and the athlete's ability to safely return to contact sport participation may be considered. Although rare, with likel size proper maneuvers to reduce accidents.

Particularly in foot- ball, but also in other sports, offseason neck-strengthening ex- ercises are a vital part of the injury prevention programs. Improvements in equipment design and manufacture have also made great strides for safety in athletic competition, and future developments may prove beneficial in injury reduction.
The cervical spine is made up of seven specialized vertebrae, which together provide a wide range of motion to the head. As with other joints, the large range of motion afforded by the cervical spine comes at the cost of stability, as the cervical region has relatively little intrinsic bony stability and relies on ligamen- tous restraints to avoid excessive or pathologic mobility.

The upper cervical spine is especially critical to overall mobility as approx- imately one half of the flexion/extension arc is achieved by the atlanto-occipital articulation, and approximately one half of the neck rotation occurs between the atlas and axis.

Each segment of the subaxial spine allows for coupled rotation and lateral bending, due to the unique shape of the uncovertebral articulation and facet joints, which further increases the functional range of cervical motion.

Due to the low level of intrinsic stability, both static and dynamic restraints play an important role in preventing excessive mobility of the neck.

The primary static stabilizers include the anterior longitudinal ligament, intervertebral disc, posterior longitudinal ligament, ligamentum flavum, facet capsules, and interspinous and supraspinous ligaments. Important dynamic stabilizers consist of the sternoclei- domastoid, trapezius, strap muscles, and paraspinal muscles.

This muscular envelope functions as a dynamic splint and protects the cervical spine during the full arc of motion, whereas the ligamentous structures act as a checkrein, limiting motion at the end points.

The bony anatomy of the subaxial cervical spine has minimal dimensional changes, except at C7, where the anatomy is transitional between the cervical and thoracic spine. The lamina of the vertebrae blend into the lateral masses, which lie between the superior and inferior articular surfaces of the respective vertebra [3].

The inferior and superior articular surfaces of adjacent vertebrae form the facet joints, which are angled approximately 45° cephalad from the transverse plane. The joint capsules surrounding the facets are richly innervated by proprioceptive and pain receptors [3].
Muscle strains generally occur as the result of a blow to the head or neck during the muscular contraction. The applied force often creates an eccentric contraction that causes microscopic or gross tensile failure, often at the myo- tendinous junction.

Muscles with high ratios of type II or fast-twitch muscle fibers demonstrate a higher risk for strains or shearing injuries [4]. Following a strain injury, the healing process can be divided into three stages, beginning with hematoma formation, myofibrillar necrosis, and the initiation of the inflammatory response, referred to as the destructive phase [5].

The next phase has been termed the repair phase and involves phagocytosis of necrotic tissue and regeneration of myofibers, and the formation of fibrous tissue in areas of damage. The final phase is called remodeling and entails maturation of the regenerated muscle tissues and reorganization of scar tissue according to the stresses placed on the zone of injury.
Injuries to the facet joints and capsular ligaments have been blamed for chronic neck pain following forced flexion injuries such as whiplash [6].

Anatomical studies have identified encapsulated mechanicoreceptors in the cervical facets, which provide proprioceptive information from the cervical spine [7]. These mechanoreceptors provide pain perception from the articulation and are theorized to play a significant role in protective muscular contraction in response to unexpected external forces.

Whiplash injuries may lead to damage of the cartilaginous surfaces of the facet joints, traumatic cervical disc herniations, and premature degenerative changes. The chronic pain experienced by some individuals following a cervical whiplash injury may be the result of injury to both the facet joints and intervertebral discs [8].

Panjabi et al simulated a whiplash trauma in cadaveric spines in an attempt to explain the role of cervical capsular ligaments during whiplash injuries [9]. Although their biomechanical study demonstrated only moderate capsular stretching, the authors theorized that cervical capsules would be subjected to significantly greater forces with the addition of coupled cervical rotation during real-life scenarios.

Children are at elevated risk for clinically significant ligament sprains, due to differences in the shape of the cervical facets and their inherent ligamentous laxity. McGrory et al, in a review of cervical spine injuries in pediatric patients, noted an increase in ligamentous injuries in children under age 11 compared with older adults [10].

The authors noted that the immature facets and uncinate processes were less effective in resisting pathologic motion, thus subjecting the ligamentous structures to a larger role in maintaining stability [10]. Hill et al reported similar findings and emphasized the presence of ligamentous disruptions in the upper cervical segments [11].

The predilection of upper cervical disruptions seems to be due to intrinsic ligimentous laxity in children, coupled with poorly developed musculature and immature osseous anatomy [10].
Typically, patients sustaining a cervical sprain, strain, or contusion present with painful, limited cervical motion and tenderness over the involved structure.

Athletes with these symptoms must be evaluated radiographically to rule out clinically significant fractures or instability patterns. It is vital to obtain adequate- quality plain radiographs in at least two orthogonal planes of the entire cervical spine (occiput to C7-T1 junction). Webb et al provided several radiographic signs that were found to be indicative of cervical instability [12].

These signs included: (1) interspinous widening, (2) vertebral subluxation, (3) vertebral compression fracture, and (4) loss of cervical lordosis. White et al, using ligament sectioning studies, identified the presence of radiographic horizontal displacement of 3.5 mm or angular displacement of 11° or more angular as signs of instability [13].

The term subacute instability was coined by Herkowitz et al, who presented a series of patients with initial normal radiographs that were subsequently found to have unstable cervical injuries [14]. This condition was hypothesized to result from the presence of muscle spasm that masked the initial instability on radio- graphs [14].

To avoid overlooking these injuries, the authors recommended maintaining immobilization until the resolution of initial muscle spasm, allowing good quality radiographs to be obtained.

Recent studies have investigated the use of magnetic resonance imaging (MRI) to diagnose and define ligamentous injuries in the cervical region.

A recent prospective multicenter study concluded that MRI identified 100% of the cervical ligamentous and spinal cord injuries in patients being evaluated for cervical spine trauma [15]. Because of the high degree of sensitivity for soft tissue injuries, some authors have suggested that MRI provides the optimal method for investigation of the cervical region following a serious injury [16].
The management of cervical sprains, strains and contusions is similar. In the early postinjury period the neck should be immobilized and a complete clinical and radiographic examination should be performed. Minor injuries benefit from continued immobilization, rest. and analgesic or anti-inflammatory med- ication. A cervical collar is used at least until muscle spasm has subsided (often at 7-10 days) and adequate dynamic radiographs can be taken to rule out more serious instability patterns.

If the dynamic studies are negative, the collar can be weaned and gentle range-of-motion and isometric strengthening exercises can be instituted. Prolonged immobilization leads to atrophy and deconditioning of the healthy muscle fibers [4]. As the patient improves clinically, functional and sports-specific exercises are instituted.

Return to play is allowed when all symptoms of the cervical sprain or strain have resolved and full strength range-of-motion and sport-specific neck function have been regained. Even after return to sports, it is imperative that the athlete maintain a regular cervical conditioning program to minimize risk of injury recurrence.

The role of specific orthosis and formal physical therapy in preventing or decreasing the incidence of reinjury following a cervical sprain or strain is controversial.

Borchgrevink et al, in a prospective study, found no difference between patients with forced flexion-extension trauma who received immediate immobilization and physiotherapy and patients instructed to resume activities as tolerated [17].

Sport-specific orthosis, particular in football, has been used empirically for many years with the thought that it limited excessive motion and thus decreased the risk of injury.

Hovis et al demonstrated that commonly used cervical orthoses were competent in limiting hyperextension of the cervical spine, while allowing enough extension to prevent axial loading
injuries [18].
Cervical disc injuries and herniations in the athlete are less common than lumbar disc injuries and usually affect older athletes. Albright et al noted an increased incidence of cervical disc disease in high-performance athletes par- ticipating in football and wrestling compared with the general population [22].

In contrast, Mundt et al concluded that athletes participating in noncontact sports might actually be protected against the development of cervical or lumbar disc herniation [23]. The mechanism of this apparent protection was hypothesized to be due to improved muscular conditioning that protected the disc from pathologic stresses placed on the spine.

Cervical disc disease is traditionally classified as either soft- or hard-disc disease. Soft-disc herniation refers to an acute process in which the nucleus propulus herniates through the posterior annulus, resulting in signs and symptoms of cord or nerve-root compression.

Acute cervical disc disruptions that occur as a result of sports participation have been hypothesized to result from uncontrolled lateral bending of the neck [22]. Hard-disc disease generally represents a more chronic, degenerative process with a diminished disc height and the formation of marginal osteophytes. The degenerative spectrum of disc disease probably begins early in life and proceeds through a series of recognizable steps preceding most if not all symptomatic disc herniations [23].

Athletes with symptomatic disc degenerative and acute disc herniations most often present with varying degrees of neck or arm pain. Although the types of symptoms are similar in athletes and nonathletes, the symptoms of herniation may be more pronounced in athletes, due to the demands of the specific sport [23].

As with nonathletes, the initial treatment for almost all herniated cervical discs in athletes should be nonoperative. Useful treatment modalities include rest, activity modification, anti-inflammatory medication, immobilization, cervical traction, and occasionally therapeutic injections. Only in rare situations involving myelopathy or a progressive neurologic deficit should surgery be contemplated during the initial 6 to 8 weeks of symptoms.

In most athletes, the acute radicular symptoms will begin to subside in this initial period. As the symptoms improve, gentle exercises can gradually be instituted, emphasizing isometric strengthening and cervical range of motion, followed by sports-specific exercises and drills. Sporting activities can be restarted when the athlete is asymptomatic and has regained full strength and mobility.

In the minority of cases, symptoms of arm pain may persist despite conservative measures. In these cases, surgery is a reasonable consideration. Surgical treatment can be successfully undertaken from either an anterior or posterior approach.

Although some have suggested that an athlete may achieve a quicker recovery following laminoforaminotomy without fusion, a direct com- parison between athletes undergoing the two types of surgery remains to be performed [23].

Determining return-to-play criteria following surgery remains more of an art than a science. Experts have suggested, however, that following a posterior disc procedure, athletes can return to play when they are asymptomatic and have regained full strength and mobility [23]. Following anterior discectomy and fusion at up to two levels, return to play can be considered following successful fusion and rehabilitation.

Lower level cervical fusions are at less risk when compared with more proximal cervical fusions, due to the ability of the fusion mass to distribute and absorb cervical stresses [24].

Patients with longer fusions are generally considered to be at risk for returning to contact sports, and therefore the participation of these athletes is individualized.
Although spinous-process fractures often occur as an isolated injury, vigilance should be maintained to rule out a more severe injury pattern.

The lower cervical and upper thoracic regions are the most commonly involved spinal segments (Fig. 1). Several mechanisms have been described in the literature that produce isolated spinous-process fractures. The most common etiology involves a strenuous contraction of the trapezius and rhomboid muscles, which avulses the spinous process [27].

Another mechanism resulting in spinous-process fractures is a hyperflexion or hyperextension injury to the neck, resulting in avulsion of the spinous process by the supraspinous and interspinous ligaments. This second mechanism is most common with high-energy trauma, such as a motor vehicle accident, but can also occur during contact sports such as football, gymnastics, and hockey [27].

A less common mechanism described in the literature entails a direct blow to the spinous process.
Isolated spinous-process fractures are benign and heal without significant residual morbidity.

Treatment of isolated spinous-process fractures consists of cervical collar immobilization for pain relief. Range of motion is withheld until the fracture site is nontender, often within 4 to 6 weeks, at which time dynamic radiographs (flexion/extension) can be performed.

Although motion can begin if no instability is present, the athlete should undergo a full course of cervical rehabilitation before returning to formal contact sports.
Recently, an infomercial promised its audience that the advertised piece of exercise equipment would give anyone an "attractive core."

There are unfortunate, and at times hu- morous, misconceptions associated with core muscle training and the idea of someone having an attractive trans- versus abdominis or attractive multi- fidus muscle.

To the trained eye, it was apparent that these advertisers were referring to the potential chis- eled appearance of the rectus abdo- minis and perhaps external obliques, but similar to many misperceptions, these individuals did not have a com- plete understanding of what the core truly is. At times, the same confusion is noted in the exercise physiology, fit- ness, and strength and conditioning professions.

The confusion runs from the specific anatomy of the core with regard to defining what it truly is, to whether particular exercises are de- signed to enhance core strength or core stability, to the definition of core exercise, to its separation from func- tional exercise, and finally to the ef- fects of core training on performance outcomes.

Many times this confusion is as simple as pure semantics and/or differences in terminology, but in any case, the confusion does more to di- vide the misunderstood topic than it does to combine research areas and training strategies. Using available re- search, this article attempts to educate the readership on an extremely popu- lar, but controversial, topic.

In hopes of eliminating much of the confusion associated with the core musculature, the specific intent of this article is to provide an idea of where current core research resides, thereby enabling di- rection for future scientific research and application in the strength and conditioning fields.
t is wise to begin this section by describ- ing a general foundational overview of the core, and then discuss the differ- ences between core strength and core stability. The "core musculature" can be defined generally as the 29 pairs of mus- cles that support the lumbo-pelvic-hip complex in order to stabilize the spine, pelvis, and kinetic chain during func- tional movements (26). The core is also commonly referred to as the "power- house" or the foundation of all limb movement (1).

These muscles are theo- rized to create this foundation for move- ment through muscle contraction that provides direct support and increased intra-abdominal pressure to the inher- ently unstable spine (10, 25, 33, 61). To ensure stability of the spine in order to produce force and to prevent injury, trunk muscles must have sufficient strength, endurance, and recruitment patterns (10).

Strength," in reference to this article, can be defined as the ability of a muscle to exert or withstand force. Active con- trol of spine stability, in this case, is achieved through the regulation of this force in the surrounding muscles (16). When instability is present, there is a ailure to maintain correct vertebral alignment, or, in other words, a failure in the musculature to apply enough force to stabilize the spine. So, "stabili- ty" describes the ability of the body to control the whole range of motion of a joint so there is no major deformity, neurological deficit, or incapacitating pain (51, 53).

In general, the goal of the core musculature is to stabilize the spine during functional demands, because the body wants to maximize this stability (1, 16). This level of stability and kinematic response of the trunk is determined by the mechanical stability level of the spine and the reflex response of the trunk muscles prior to force being ap- plied to the body (16).

Limb movement provides exertional force onto the spine, where the magnitude of reactive forces is proportional to the inertia of the limb (35, 37), whereas coactivation of the ag- onistic and antagonistic trunk muscles work to stiffen the lumbar spine to in- crease its stability (16).

There is a con- cern, which is discussed later, that too much strength or force from core mus- culature actually can cause greater insta- bility if it is not directed correctly. Also, there is evidence to support that en- durance is the more important training variable when it comes to the core mus- culature (46, 47).

With a general understanding of the goal of the core musculature to stabilize the spine against forces, one can begin to sep- arate the confusion between the terms "core stability" and "core strength," de- spite the limited research. When the term "core stability" is used, reference is being made to the stability of the spine, not the stability of the muscles them- selves. Within the research, there has been no reference to enhancing the sta- bility of a muscle, but rather its ability to contract.

When the term "core strength" is used, reference is being made to the ability of the musculature to stabilize the spine through contractile forces and intra-abdominal pressure. Cholewicki and colleagues confirm that "active con- trol of spine stability is achieved through the regulation of force in the surrounding muscles.

Therefore, coacti- vation of agonistic and antagonistic trunk muscles stiffens the lumbar spine and increases its stability" (16, p. 1380). Increases in muscle activation potentially lead to greater spinal stabili- ty. In the same vein, confusion also may arise as to whether a given exercise is a core-strength or a core-stability exercise.

Core exercises do not aim to increase the stability of the musculature, but rather aim to enhance the muscles' ability to stabilize the spine, particularly the lum- bar spine. The confusion between core strength and core stability may be clari- fied further with a proper understanding of the anatomy of the core musculature.
Leonardo da Vinci first described the concept of muscle grouping around the spine. He suggested that the central muscles of the neck stabilized the spinal segments, whereas the more lateral mus- cles acted as guide ropes supporting the vertebrae (18).

Bergmark first classified the muscles acting on the lumbosacral spine as either "local" or "global" (9). Scientific modifications have been made to these initial classifications (1, 51). The local and global muscles can be cat- egorized according to the varying char- acteristics between them (Table 1).

The ocal musculature (Table 2) includes the transversus abdominis (TrA), multi- fidus, internal oblique, medial fibers of external oblique, the quadratus lumbo- rum, diaphragm, and pelvic floor mus- cles (61, 64). These muscles have shorter muscle lengths, attach directly to the vertebrae, and are primarily responsible to generate sufficient force for segmen- tal stability of the spine (10, 26, 61).

Re- cent research has promoted the TrA and multifidi as the primary stabilizers of the spine (26, 50, 51). The TrA is the deep- est of the abdominal muscles, originat- ing at the iliac crest, inguinal ligament, and thoracic and lumbar spinous processes via the thoracolumbar fascia, then attaching anteriorly at the linea alba (49, 61).

When contracted, it is able to increase tension of the thora- columbar fascia and increase intra-ab- dominal pressure, which increases spinal stiffness in order to resist forces acting on the lumbar spine (26, 52, 61).

The multifidi attach from the vertebral arch- es to the spinous processes spanning from sacral to cervical spine. Each mus- cle spans 1-3 vertebral levels, thus pro- viding the largest contribution to inter- segmental stability (61).

Because of their short moment arms, the multifidi are not involved with gross movement (1). The TrA and multifidi have been found to activate prior to limb move- ment in an attempt to stabilize the spine for that movement (33-38).

The TrA has been shown to activate up to 100 milliseconds before the activation of limb musculature during limb reaction time tests (30). The TrA, specifically, is activated regardless of direction of limb movement (26, 33-36, 38). This activa- tion promotes spinal stability no matter the direction and begins to confirm the primary stabilizing function of the TrA.

Due to the lone stabilization functions of the TrA and multifidi, the local system can be divided into primary and sec- ondary stabilizers (Table 2).

The primary stabilizers are the TrA and multifidi, be- cause they do not create movement of the spine. The internal oblique, the medial fibers of the external oblique, and the quadratus lumborum function primarily to stabilize the spine, but also function secondarily to move the spine (51). psoas major, and the erector spinae. Tra- ditional exercises such as the sit-up have focused on enhancing the capacity of this global musculature.

It is thought that exercises that produce gross move- ment of the spine, such as the sit-up, emphasize the global system and not the local system. These exercises emphasize the global systems, not isolate the global systems, because both systems theoreti- cally work in synergism (17).

With ref- erence to fiber typing, the local system comprises mainly type I fibers, whereas the global system mainly consists of type II fibers (57, 61). It should be noted here that there are other, less researched muscles not labeled in the classification of local and global musculatures, and these classifications may vary with new and much needed discoveries from re- search investigations.

With the lack of current research in this area and most in- vestigations using populations with variations of low back pain, it is difficult to make assumptions regarding the ap- plication of the core musculature to the strength and conditioning populations. Nonetheless, these assumptions are made.
Core and lumbo-pelvic-hip stabiliza- tion research began by investigating in- dividuals with low back pain, chronic
low back pain, spondylolysis, and spon- dylolisthesis (22, 23, 34, 51, 52, 57, 59, 64, 66).

It has been shown that in individuals with low back pain and lumbar instability, local stabilizing muscles, including the TrA, are affected preferentially, resulting in inefficient muscular stabilization of the spine (33-37, 52). Although in in vivo porcine studies, Hodges and colleagues have shown the TrA to increase intra- abdominal pressure, thus reducing lumbar intervertebral displacement and increasing lumbar stiffness (33).

Despite the lack of in vivo TrA research in humans, other research has been able to create a strong theory of its impor- tance, along with the other local mus- cles, in stabilizing the spine (1, 9, 16, 22, 27, 33-38, 43). The core muscula- ture becomes especially important as the application of forces onto the spine during events of life and sport chal- lenges the musculature's ability to sta- bilize and protect the spine.

As previously stated, the spine is inher- ently unstable. The ligamentous spine (stripped of muscle) will fail or buckle under compression loads of as little as 2 kg or 20 N (10, 46). Level walking can produce up to 140 N of compression force to each side of the spine with each step (20). Holding an 80-lb object in front of the body while standing in neu- tral posture will produce large compres- sion forces of 2,000 N at the lower lum- bar levels (24).

Compression was found to be 3,230 N for straight-leg sit-ups and 3,410 N for bent-knee sit-ups, whereas shear forces were 260 and 300 N, respectively (47). Rowing has been shown to produce peak spinal compres- sion forces on the spine of 6,066 N for men and 5,031 N for women (3).

Foot- ball blocking has been shown to produce average compression forces, anteropos- terior shear forces, and lateral shear forces of 8,679 ± 1,965 N; 3,304 ± 116 N; and 1,709 ± 411 N, respectively (28). Half-squat exercises with barbell loads in the range of 0.8-1.6 times body we has been shown to activate up to 100 milliseconds before the activation of limb musculature during limb reaction time tests (30).

The TrA, specifically, is activated regardless of direction of limb movement (26, 33-36, 38). This activa- tion promotes spinal stability no matter the direction and begins to confirm the primary stabilizing function of the TrA.

Due to the lone stabilization functions of the TrA and multifidi, the local system can be divided into primary and sec- ondary stabilizers (Table 2). The primary stabilizers are the TrA and multifidi, be- cause they do not create movement of the spine.

The internal oblique, the medial fibers of the external oblique, and the quadratus lumborum function primarily to stabilize the spine, but also function secondarily to move the spine (51).
The muscles primarily in charge of pro- ducing movement and torque of the spine are the global muscles (Table 2).

Global muscles (sometimes categorized as "slings") possess long levers and large moment arms, making them capable of producing high outputs of torque, with emphasis on speed, power, and larger arcs of multiplanar movement, while countering external loads for transfer to the local musculature (26, 61).

These muscles include the rectus abdominis, lateral fibers of the external oblique psoas major, and the erector spinae. Tra- ditional exercises such as the sit-up have focused on enhancing the capacity of this global musculature. It is thought that exercises that produce gross move- ment of the spine, such as the sit-up, emphasize the global system and not the local system.

These exercises emphasize the global systems, not isolate the global systems, because both systems theoreti- cally work in synergism (17). With ref- erence to fiber typing, the local system comprises mainly type I fibers, whereas the global system mainly consists of type II fibers (57, 61). It should be noted here that there are other, less researched muscles not labeled in the classification of local and global musculatures, and these classifications may vary with new and much needed discoveries from re- search investigations.

With the lack of current research in this area and most in- vestigations using populations with variations of low back pain, it is difficult to make assumptions regarding the ap- plication of the core musculature to the strength and conditioning populations. Nonetheless, these assumptions are made.
Core and lumbo-pelvic-hip stabiliza- tion research began by investigating in- dividuals with low back pain, chronic
low back pain, spondylolysis, and spon- dylolisthesis (22, 23, 34, 51, 52, 57, 59, 64, 66). It has been shown that in individuals with low back pain and lumbar instability, local stabilizing muscles, including the TrA, are affected preferentially, resulting in inefficient muscular stabilization of the spine (33-37, 52).

Although in in vivo porcine studies, Hodges and colleagues have shown the TrA to increase intra- abdominal pressure, thus reducing lumbar intervertebral displacement and increasing lumbar stiffness (33).

Despite the lack of in vivo TrA research in humans, other research has been able to create a strong theory of its impor- tance, along with the other local mus- cles, in stabilizing the spine (1, 9, 16, 22, 27, 33-38, 43). The core muscula- ture becomes especially important as the application of forces onto the spine during events of life and sport chal- lenges the musculature's ability to sta- bilize and protect the spine.

As previously stated, the spine is inher- ently unstable. The ligamentous spine (stripped of muscle) will fail or buckle under compression loads of as little as 2 kg or 20 N (10, 46).

Level walking can produce up to 140 N of compression force to each side of the spine with each step (20). Holding an 80-lb object in front of the body while standing in neu- tral posture will produce large compres- sion forces of 2,000 N at the lower lum- bar levels (24).

Compression was found to be 3,230 N for straight-leg sit-ups and 3,410 N for bent-knee sit-ups, whereas shear forces were 260 and 300 N, respectively (47). Rowing has been shown to produce peak spinal compres- sion forces on the spine of 6,066 N for men and 5,031 N for women (3).

Foot- ball blocking has been shown to produce average compression forces, anteropos- terior shear forces, and lateral shear forces of 8,679 ± 1,965 N; 3,304 ± 116 N; and 1,709 ± 411 N, respectively (28).

Half-squat exercises with barbell loads in the range of 0.8-1.6 times body weight applied variant spinal compressive loads between 6 and 10 times body weight (13). In other words, a 200-lb athlete lifting a barbell loaded to 320 lbs during a half-squat would be applying 2,000 lbs or almost 8,900 N of compres- sive force onto the lumbar spine.

Cholewicki, McGill, and Norman showed that the average compressive loads on the L4-L5 joint of powerlifters were estimated to be up to 17,192 N (15). Extreme lifting also has been shown to produce loads on the lumbar spine of up to 36,400 N (29).

These types of compressive loads at the lumbar spine, from life and sport, ex- ceed those loads determined during fa- tigue studies to cause pathologic changes in both the lumbar disk and the pars interarticularis, which contribute to conditions such as spondylolysis (28).

Spine compression and lateral shear forces also have been shown to in- crease as the lift origin becomes more asymmetric, with one-hand lifting changing the compression and shear profiles significantly (44). This knowl- edge is valuable, because much of life and sport requires not only extreme loading of the spinal musculature, but also varying angles, positions, and speeds.

This understanding of the mul- tiplanar forces that life and sport place on the spine and the injury that could ensue have prompted individuals to seek methods to train the strength or stabilizing capacity, endurance, and neuromuscular reactive properties of the core musculature. It has been sug- gested that focus should move past strength alone to understand the speed with which the muscles contract in re- action to a force (51).

It also has been suggested that an individual who demonstrates strong performance on a strength test of force may not necessari- ly display an equally strong perfor- mance on a test of endurance (43). The individual's history and the specificity of training should dictate the outcomes of assessment tools and subsequent training emphasis.

As with other mus- cular assessment, measures of the core should include various performance measures of force, endurance, and power. This area, among many others, is one of needed future research.
There is limited research on the assess- ment of core musculature, which adds to some of the confusion associated with this topic. Clinically, core activa- tion has been measured with ultra- sound, magnetic resonance, and elec- tromyography (3, 33-38, 50, 54, 64).

One of the limitations in the clinical di- agnosis of lumbar instability revolves around the difficulty to accurately de- tect abnormal or excessive intersegmen- tal motion, with conventional radiolog- ic testing often reported as being insensitive and unreliable (52). There could be possible advancements in these areas, but current research with the core musculature is lacking, to the authors' knowledge.

Progress has been made to- ward simpler assessments of the core musculature, with growing knowledge of abdominal hollowing aiding this progress. Abdominal hollowing is specif- ically the cocontraction of the local sys- tem, especially the TrA, multifidi, inter- nal oblique, diaphragm, and pelvic floor musculature, while an individual isometrically contracts and draws in the abdominal wall or navel without move- ment of the spine or pelvis (5, 19, 22, 52, 56, 57, 59, 60, 63).

This drawing-in maneuver is designed to emphasize the deep local muscle activity, because there is minimal activation of the more super- ficial global muscles, such as the rectus abdominis (51).

It has been shown that abdominal hollowing, rather than the sit-up movement, activates a cocontrac- tion mechanism of the TrA, multifidus, and internal obliques, rather than the rectus abdominis and external obliques, with increased activation of the TrA when lumbopelvic motion is limited (56, 59, 63).

Abdominal hollowing also has been shown to increase the cross- sectional area of the TrA (19). The re- search of abdominal hollowing provides important feedback as to the design of uture core assessment programs by il- lustrating that many exercises that may be performed as core exercises do not preferentially activate the local stabi- lization system of the core, but rather emphasize the global musculature.

A growing number of researchers, howev- er, have concerns that abdominal hol- lowing during exercise can actually cause injury and should not be advocat- ed. The newer suggestion for athletes appears to be the abdominal bracing technique. This growing controversy is discussed in more detail in the next sec- tion.

This focus on activating the stabiliza- tion system of the core is thought to carry into future prescription for ath- letes as well. As it is, the most commonly utilized assessments and training are done in the supine or prone position. They are designed to assess or to train the stabilizing system with minimal acti- vation of the movement system, but a question arises when athletes do not typ- ically require spinal stabilization in a supine or prone position.

Athletes and other individuals must be concerned with spinal stability, including abdomi- nal hollowing, with the effects such as gravity, external forces, and momentum. To the authors' knowledge, there is no current, valid test for the core muscula- ture in a plane or position other than supine and prone, along with limited re- search in quantifying the activation of both stability and global systems in the athlete.

Assuming the law of specificity applies to the core musculature as well, it may be beneficial for future research to assess and to quantify the activation of the stabilization system in positions more specific to a given sport, function, or action.

Posterior pelvic tilting also has been ad- vocated to cause cocontraction of the local stabilization musculature.

Never- theless, it is not suggested at times due to the increased activation of the rectus abdominis and speculation of negative often cause low back pain (22). For the pelvic tilt to be performed, the individ- ual contracts the lower abdominal mus- cles to rotate the pelvis posteriorly, so that the lumbar spine flattens out.

A common posture is hyperlordotic, which tilts the pelvis anteriorly or for- ward and is associated with the imbal- anced lengthening of the abdominal muscles and gluteals combined with shortening of the hip flexors that may lead to lack of accurate segmental con- trol (51).

Researchers investigating simpler forms of core strength (its ability to stabilize) and endurance assessments have utilized these findings supporting the cocontrac- tion effects of abdominal hollowing on the local stabilization musculature.

Ab- dominal hollowing, especially in the supine position, has been shown to in- crease the activity of the TrA (8, 63). In response to this notion, researchers have begun to utilize an inflatable biofeed-preload effects on the lumbar spine that back transducer placed under the lum- bar spine in this supine position.

TrA ac- tivation decreases as lumbopelvic move- ment increases, and thus stability of the spine can then be measured indirectly through changes in the pressure applied to the transducer (63). A common test utilizing this biofeedback transducer, as well as increased spine stabilization de- mands with lumbopelvic motion, is a modified Sahrmann lower abdominal assessment (1, 62).

The Sahrmann assessment protocol is il- lustrated in Table 3 and begins in the supine crook-lying position. Strength, endurance, and stability at the lumbar spine with the varying protocols, in- cluding the Sahrmann scale, are assessed using an inflatable pressure tranducer or cuff, such as the Stabilizer (Chattanooga Pacific Pty. Ltd., Brisbane, Australia) (61). With the Sahrmann core stability test, the transducer is placed under the individual's lumbar spine while he or she s lying supine in a hook-lying position.

The transducer then is inflated to 40 mm Hg, while the individual activates the stabilizing musculature via the ab- dominal hollowing technique. Abdomi- nal hollowing, if performed correctly, will result in either no change in pres- sure or a slight decrease from the initial 40 mm Hg (22).

There are 5 levels in the Sahrmann test. In order to advance to a new level, the lumbar spine position must be maintained, as indicated by a change of no more than 10 mm Hg in pressure on the analog dial of the pres- sure biofeedback unit (62). Pelvic tilt with its flattening of the lumbar spine onto the cuff will increase the pressure reading.

This pelvic tilting will increase the pressure transducer to a point where it does not move, thus indicating that the lumbar spine has maintained stabili- ty (61). The Sahrmann protocol could possibly be used as a scientifically based protocol that indirectly tests the ability of the core musculature to stabilize the spine with and without motion of the lumbopelvic complex.

This protocol may provide an easier means for future research to pre- and posttest the effects of training on the core musculature. Nevertheless, there is important re- search needed to validate the effective- ness of this assessment in varying popu- lations, as well as research investigating muscle activation and its application to performance.
Research has begun to further quantify the muscles that contribute to stability under spinal load, expanding on the few studies that have been done in this area (39, 40, 41).

In other words, these re- searchers seek to determine how much muscular stiffness is necessary for stabil- ity (11, 14, 47), typically by placing a numeric value to activity, compression, and resultant stability.

Activation pat- terns are measured while certain exercis- es are performed at different spinal loads, and these patterns are quantified using advanced biomechanical models Extensive discussion of these bio- mechanical models is out of the scope of this article, but the growing area of re- search has brought valuable information to the strength and conditioning profes- sion in regard to abdominal exercise pre- scription.

As stated previously, much research has proposed the TrA as a major contributor to spinal stability and has suggested ab- dominal hollowing or "drawing-in" as a way to activate the TrA with minimal ac- tivation of the rectus abdominis and other global muscles. Abdominal hol- lowing has been shown to increase the thickness of the TrA (19) and promotes greater sacroiliac joint stability (59).

Be- cause most of this research, however, has been performed with patients with low back pain, questions have arisen regard- ing its application to a healthy individ- ual or advanced athlete. Many scientists now suggest that a more suitable method of stabilizing the spine may be abdominal bracing, due to its ability to cocontract more abdominal muscles, in- stead of one muscle, such as the TrA, being activated for stability (40).

Vera- Garcia and colleagues showed that coac- tivation of all trunk abdominal muscles (abdominal bracing) increased the sta- bility of the spine and reduced lumbar displacement after loading. All the torso muscles appear to play an important role in securing spinal stability and must work together to accomplish this stabili- ty.

Many of these same scientists dis- agree with abdominal hollowing and the attempt to singularly activate the TrA and multifidus before dynamic, athletic movements. Hollowing or drawing-in may decrease activation of many mus- cles that are normally active during dy- namic movements, thus preventing the natural abdominal cocontraction of all musculature.

Not only has the interpretation of the scientific literature caused confusion of proper abdominal activation technique (abdominal hollowing, drawing-in, or abdominal bracing), but these terms
have been misconstrued. There are many popular fitness facilities, to remain un- named, that teach the drawing-in ma- neuver to their trainers for subsequent prescription to clients.

They use the term "draw-in" to describe the inward move- ment of the abdomen with abdominal contraction, similar to the feeling when all air is expelled forcefully. The activa- tion of the TrA will create a pull inward against the abdominal viscera, thus being a strong muscle of exhalation and expul- sion (32).

By forcefully expiring all of one's air, the activation of the TrA is thought to be optimal and the client can experience the proper sensation of the tight abdominals during the drawing-in maneuver. In this case, the sensation of abdominal activation may simulate that of abdominal bracing. Richardson and Jull (58) originally described drawing-in by asking patients to "gently draw in the abdominal wall especially in the lower abdominal area."

Abdominal hollowing or drawing-in has been defined further as the isometric contraction of the abdomi- nal wall without movement of the spine or pelvis (22) or as placing emphasis on anterolateral abdominal muscle activity over the rectus abdominis by drawing the navel up and in toward the spine (2).

The draw-in maneuver is described different- ly than the abdominal bracing tech- nique, in which more of the external obliques are activated (58). Abdominal bracing has been described more specifi- cally as coactivation of all the abdomi- nals (2, 65) or as lateral flaring of the ab- dominal wall (42, 63).

The drawing-in or abdominal hollowing maneuver may be better suited for static exercises that focus on training the local system, but may be a poor suggestion for activating abdominals during performance tasks where the global system must be active. Conversely, abdominal bracing is not ap- propriate if the aim of the exercise is to preferentially activate the TrA or the in- ternal obliques (63).

It seems that hol- lowing is being suggested currently for greater TrA activity in a supine position with low back pain patients, whereas ab- dominal bracing may be more suitable or more dynamic movements and exter- nal loading. It has been noted previously that future research will need to investi- gate whether or not these types of static exercises translate to multiplanar, dy- namic situations.

Not only has controversy arisen over what type of abdominal activation is op- timal for spinal stability, but research has begun to examine the potentially harmful effects of too much stability, in addition to those of too little stability.

Sufficient stability of the lumbar spine can be achieved for a neutral spine in most people with modest levels of coac- tivation of the abdominal wall (47). This "sufficient stability" would be the minimal level to assure spinal stability without imposing unnecessary loads on the muscles and associated tissues (65).

Because it appears that endurance may be more important than strength and should be trained before strength, train- ing may be better focused toward re-ed- ucating faulty motor control systems (46, 47) rather than toward stabilization system strength, which may cause inap- propriate force to the spine.

Currently, there seems to be no such thing as an ideal set of exercises for all in- dividuals, but there are general sugges- tions for exercises that emphasize trunk stabilization in a neutral spine, while also emphasizing mobility at the hips and knees (4, 6, 47).

Based on his quantify- ing research, McGill (46) has suggested the proper order of exercises to be the cat stretch exercise, anterior abdominals and curl-ups with hands under the spine to help maintain a neutral spine, lateral musculature activation with side bridges, and finally, extensor exercises like the bird dog (4-point kneeling, opposite arm, opposite leg raise) exercises.

McGill has made further suggestions that the ideal exercise would challenge the mus- cle while imposing minimum spine loads with a neutral posture and elements of whole body stabilization (47, 48). Cau- tion should be used when implementing whole body stabilization as a pure core exercise, because scientific observations have not correlated balancing while standing on an unstable surface to train- ing spinal stabilizers (12).

Future re- search should begin to examine the spinal stabilizers during these popular exercises and to quantify loads on the spine during real-time, real-life activi- ties. How do the loads presented in quantification studies compare with the exercises and performance tasks of ath- letes?

This research would fall in line with suggestions of utilizing core exercis- es while standing, because specificity would suggest such exercises to mimic the demands of life and sport. Imple- mentation of core applications and/or advanced abdominal exercises and being infused into fitness and sport perfor- mance protocols more rapidly than valid research is being conducted.

Quantifica- tion of the core appears to be a valid area of future research for the strength and conditioning or fitness professional to stay up-to-date and to utilize in future prescriptions.
The main purposes of basic core strength training (training the local sys- tem) is to increase stability and to gain coordination and timing of the deep ab- dominal wall musculature, as well as to reduce and prevent injury (26, 66). Most of the research done on the appli- cation of the core musculature has fo- cused on limited bouts in order to exam- ine activation only.

There has been an enormous media frenzy that advocates the ability of core training to enhance performance; unfortunately, there is limited research to support these claims. Hagins and associates showed that a 4- week lumbar stabilization exercise pro- gram improved the ability to perform progressively difficult lumbar stabiliza- tion exercises (30).

Six weeks of Swiss ball training specifically designed for core activation improved the ability of the core musculature to stabilize the spine significantly, while also improving core endurance (62). Because the spine is mechanically unstable, stiffness may be decreased at one joint accompanied by muscles and a motor control system that is "unfit."

This combination results in inappropriate muscle activation se- quences when performing even relative- ly simple tasks (46). Core training seeks to coordinate the kinetic chain (muscu- lar, skeletal, and nervous systems) to en- hance the synergism and function of the core musculature. Panjabi (53) created a convenient model for the core muscula- ture, categorizing the interaction of the spine into 3 systems: passive, active, and neural.

The passive system consists of the vertebrae, intervertebral discs, zy- gapophyseal joints, and ligaments. The active system consists of the muscles and tendons surrounding and acting upon the spinal column, including both local and global muscles.

The neural system describes the central nervous system (CNS) and accompanying nerves that direct efferent and afferent control over the active system to provide dynamic stability during movement. These sys- tems work interdependently, so that one is able to make up or compensate for deficits in another (53).
The progression of training in the core musculature typically and currently works from the inside out. Training fo- cuses on optimizing the function of the local system before emphasizing move- ments that utilize the global system.

Functional progression is the most im- portant aspect of the core-strengthening program, which includes performance goals, a thorough history of functional activities, varied assessments, and train- ing in all 3 planes of motion (1, 43). As previously mentioned, the local or stabi- lizing system consists of mainly type I tonic musculature.

The type I fibers of the local stabilization system tend to weaken by sagging (51). Specificity, then, would require local system exercis- es that involve little to no motion through the spine and pelvis for the local, stabilizing muscles. Examples of these local system exercises are shown in Figures 1-7.

The local system is activated with low resistances and slow move- ments that prolong the low-intensity isometric contraction of these specific stabilizing muscles (51, 61). Because most isolation exercises of the local musculature, including the TrA, are in nonfunctional positions, exercise train- ing may need to shift to more function-
al positions and activities.

The global system, consisting of more type II fibers that create movement of the spine, may be emphasized through exercises that involve more dynamic eccentric and concentric movement of the spine through a full range of motion.

Exam- ples of these seen in Figures 8-14. The activity of
global muscles, which tend to shorten or tighten, will differ from that of the sag- ging local system (51). Rapid movement and higher resistances also will recruit these global muscles, especially the rec- tus abdominis (51).

These types of exer- cises not only emphasize the global sys- tem, but also create an environment for the local system to begin to stabilize the spine in varying, multiplanar move- ments. Training the core for an emphasis in strength would include high load, low repetition tasks, while endurance en- hancement requires longer, less demand-global system exercises are ing exercises (46).

Beyond our knowl- edge of basic muscle physiology and adaptation, there is little research on the specific types of core exercises to be used and their effects on the ability of the musculature to stabilize the spine in varying planes of motion. With the lim- ited research in this area, specificity to the individual's history and goals, along with progression, should not be over- looked.
The stability of the lumbar spine is not dependent solely on the basic mor-
phology of the passive and active sys- tems, but also the correct functioning of the neuromuscular system (52).

The patterns of recruitment and relative onset times between muscles are mod- ulated by the CNS, ensuring optimal movement control, muscle perfor- mance of the core, and control of reac- tive forces produced by the limb move- ments (10, 35).

Training and exercise can lead to great increases in maximal dynamic strength through neural adaptations in all musculature, so the neuromuscular system then can specif- ically compensate and improve dynamic stability of the spine (31, 51).

More focus may be directed toward coordi- nation and timely muscle activation of the deeper local system to enhance spine stability, rather than just toward improving strength and range of mo- tion (17, 26). There are no current guidelines to accomplish these adapta- tions, emphasizing another important area for future research.

The reflex re- sponse of the stabilizing musculature to applied or produced force combines with the mechanical stability level to determine the kinematic response of the trunk (16). It also seems that some unexpected loading scenarios onto the trunk may be too fast and/or with too high of a magnitude for the reflex re- sponse to control intersegmental dis- placement effectively and safely (16).

In these scenarios, it may be more im- portant to consider that it is not the strength of the stabilizing muscula- ture, but the speed with which the muscles contract in reaction to the forces that are capable of displacing the spine (51).

Potvin and O'Brien showed that trunk muscle cocontraction in- creased firing during lateral bend con- tractions as the agonist trunk muscles fatigued (55). The investigators pro- posed that the fatigue produced by the xertions compromised neural coordi- nation and that the increased cocon- traction served to maintain stability of the spine. As with other forms of train- ing, the neural component, as well as optimal gains in musculature adapta- tion, should be considered for future research.

It also should be noted here that much emphasis has been placed on the ability of the TrA and multifidi (core stabilization system) to activate prior to the limbs and global system muscles in order to stabilize the spine against gross movement patterns.

Despite this emphasis, these differing musculatures may not work in isola- tion, but may work together to stabi- lize and move the spine. The TrA has been shown to activate independently of other core musculature to decrease activation during lumbopelvic move- ment (38, 63).

So, other musculature will activate to work together for sta- ble spine maintenance in dynamic multiplanar movements. Beneficial progression in exercises for enhancing spinal stability, then, may involve the entire spinal musculature and its motor control under various loading conditions (17).

Until research begins to shed light upon optimal progression during core train- ing, progression may be programmed according to the known frequency, in- tensity, time, and type (FITT) principle that commonly is used in select training protocols.

As with most training proto- cols, the FITT principle is utilized and manipulated to meet specific needs of the individual. This manipulation would seemingly be no different in core training practices. Common sense with knowledge of general neuromuscular adaptations can be used to manipulate these select variables, though always considering the safety of the individual first.

Frequency can be adjusted, as with any other muscle being trained, to em- phasize overload, recovery, and specifici- ty. Intensity can be progressed in exer- cises training the local and global musculatures by simply increasing the instability of the environment, foot po- sitioning, and lift progression (Table 4, Figures 13 and 14) or by increasing re- sistance by wearing a weight vest during exercises. Time or duration of exercises tends to fluctuate, depending upon the particular exercise used.

The local mus- culature exercises that require little to no movement typically require durations of 30-45 seconds, utilizing assumptions based on their type I fiber composition and stabilization duties. At the point where holding an exercise for 45 seconds is no longer challenging, progressions an be made with intensity, thus de- creasing the ability to hold the exercise for a given duration. As the individual adapts to the training progression, ad- justments again can be made through any of the other previously noted vari- ables. Research examining the alteration and progression of all training variables with the core is at its genesis and is of great importance to the advancement of the literature in this area.

Movement or global system exercises may utilize num- bered repetitions, which will be adjusted and progressed according to the specific needs of the individual. Again, the type of exercises selected fall under the prin- ciple of specificity, always considering the exercise history, current level of fit- ness, and performance goals of the per- son involved in the individually de- signed training protocol.

Further, as core training progresses, consideration always should be placed on synergistic relationships within the human body, including the ability of the 2 systems of the core musculature to work together (17). Local and glob- al musculatures work together to cre- ate dynamically stable and functional- ly efficient multiplanar movements of the spinal column.

Argument could be made that because, ideally, both sys- tems work together, training should begin to utilize this relationship and progress from there to maximize its functional transition to a specific out- come or function. Even as progression aims to challenge the core musculature in environments similar to those of competition or of life, it may be wise to begin slowly, using the specificity and FITT principles. In addition, it is commonly agreed that most individu- als overtrain the global musculature before optimal development of the local system has been accomplished.

Overtraining of the global muscula- ture before sufficiently training the local musculature is thought to create a situation where force is being pro- duced by the global muscles that can- not be controlled and handled by the local musculature. Anecdotally, this situation has been exemplified as a fast sports car with a poor braking system.

The car and its associated engine de- signed to reach high speeds represents the overtrained global system, whereas the poor braking system represents the undertrained local system. Even though the sports car can reach accel- erated velocities, the brakes are unable to properly slow it down, and thus a crash occurs. In real life, the subse- quent crash refers to maladaptive movement of the body and eventual injury to the spine.

Despite the effec- tiveness of such analogies, however, there is a lack of research to confirm the theories behind the interaction of the different systems of the core mus- culature. As with all forms of training, progression and specificity of the core musculature must be considered, and future research must seek to determine specific training's effect on perfor- mance to accomplish safe and optimal performance outcomes.
With the distinctions made between training specifically for local and global systems and having established the importance of proper, specific progression, one final area that is often confused and misunderstood will be addressed. Specif- ically, some confusion with core training arises with the mislabeling of certain ex- ercises as "core exercises."

The general definition of the word "core", as can be found in an ordinary dictionary, is "the central or most important part of some- thing." For instance, many weight train- ing protocols have a set of core exercises, such as the squat. In this case, core de- scribes the central, fundamental, or basic lifts that are needed to build upon in that particular area of training.

In this exam- ple, core does not mean that the lifts are specifically training the local and global musculature of the lumbar spine (our de- finition of core). This distinction must be made, because certain central or fun- damental exercises, such as the squat, are labeled as core exercises.

The squat will require the activation of the core muscu- lature, both local and global systems, to ensure proper spinal stability during the movement. However, the same can be said of very simple tasks as well, such as bending over to pick up a small object (46).

Picking up a small object is not considered a core exercise, even though the core musculature is activated. So, be- cause the core musculature is used in any movement that requires segmental stabi- lization and protection of the spine, con- fusion may arise if we are not careful in using the label of "core exercise." This distinction must be made, especial- ly with the rush of stability training equipment that is flooding the market.

Confusion occurs because certain de- vices and exercise protocols are adver- tised to train the core musculature.

When performing exercises on unstable surfaces, the core musculature will be challenged, but the intent of the exercise is to train the neuromuscular system by progressively challenging balance, sta- bility of the limbs, coordination, preci- sion, skill acquisition, and propriocep- tion (7, 26, 62).

These exercises also may be considered functional exercises when they are specific to the demands of an individual's sport or activity. The exer- cise does not have to be on an unstable surface, a Swiss ball, or any other piece of stability equipment to be considered functional.

On the one hand, for exam- ple, a controlled seated machine rowing exercise would be functional for a rower, because it is more specific to the athlete's goals and the seated environment of competition. On the other hand, unsta- ble environments pose very functionally based (task- and goal-specific) exercises for athletes and nonathletes alike, be- cause most sports and even activities of daily living require force production and acceptance in multiplanar, dynamically unstable environments.

For instance, a functional training mentality may pro- mote an offensive lineman to train at times with a standing cable chest press on a single leg, because many times of- fensive linemen are required to exert upper-body force on an opponent dur- ing a game while in a single-leg environ- ment. This type of exercise, like the squat, is not considered a core exercise specifically designed to train the local and global musculature of the spine.

It is a functional, sport-specific performance enhancement exercise that is individual- ized to the athlete. The core must be uti- lized in this movement, but the intent is to create an environment to train the neuromuscular system to stabilize dy- namically, to produce force propriocep- tively, and to manage force exerted on the global movement system, which will minimize the force transferred onto the local stabilization system and the spine.

In current theory, once the stability of the inner and global core musculatures have been examined and have been trained, then a progressive protocol may be added to develop the enhanced capa- bilities of the limb musculature in sport-specific training.

Again, consider- ation may need to be made as to whether or not this approach is the best in utilizing spinal stabilization in sport- specific environments. In addition, fu- ture research should examine the effec- tiveness of placing the individual in an environment that is overly unstable,such as standing on a wobble-board. Questions concerned with the amount of force production loss, the amount of neuromuscular stimulation, and its transfer from these extremely unstable environments to performance should be answered by future research in these areas.

A commonly seen progression in func- tional lift and stance progressions is shown in Table 4, with examples in Fig- ures 13 and 14. Progression is required, because as the instability of the lift or en- vironment increases, so do the demands placed upon the stabilization muscula- ture (2, 21). These functional progres- sions seek to gradually place individuals in functional environments and plat- forms that will be required of them dur- ing life or sport. Advances in the stance and lift progressions can be utilized in conjunction during training.

For exam- ple, the most stable dumbbell overhead press exercise would be with 2 feet at hip or shoulder width while pressing both arms at the same time. The most unstable format of the same exercise would be a single-leg, contralateral, single-arm press with rotation. The importance of train- ing in these environments can be seen, because there is a decrease in force pro- duction as the environment becomes more unstable (3).

Given that production and maintenance of force decreases with increasingly unstable environments, such as the offensive lineman blocking in a sin- gle-leg or staggered stance while applying force with a single arm, it may seem prac- tical and optimal to progressively train the individual's ability to produce and maintain force in these naturalistic or functional environments.

With the pro- gressive nature of functional training and its common confusion with core train- ing, careful attention may be needed in the labeling of exercises to ensure the dis- semination of terminology and future re- search in these areas.
With a growing understanding of specif- ic labeling needs and the function of the core musculature, research should begin to examine the effect of varying training programs on core strength, core en- durance, and neuromuscular adapta- tions. Furthermore, researchers could begin to examine core training's func- tional application to specific perfor- mance variables or how specific core-ex- ercise training can be applied to performance or sport-specific training. Limited research has been conducted in this area. Stanton, Reaburn, and Humphries compared core-training ef- fects on running economy (62).

After 6 weeks of Swiss ball training, despite sig- nificantly improving core musculature strength and endurance, subjects did not demonstrate any significant changes in running economy. The authors do note that these results may be applicable only to the specific population that was used for this study (male athletes, 15.5 ± 1.4 years of age).

In addition, despite participants getting stronger and scor- ing higher on the Sahrmann test with no improvement in running economy, one may question the effectiveness of uni- planar core training on multiplanar per- formance. With the lack of research re- garding the application of core training on performance, further studies should examine specific and varied training protocols' effects on performance.

Fu- ture research also should continue to validate core assessment techniques, with consideration of the specificity of the individual's history, goals, training, and prescription.

Core assessment and training also should be investigated with athletic and normal populations for standardization and application, in ad- dition to low back pain populations, with emphasis on continued validation of protocols utilizing inflatable biofeed- back transducers to measure core strength and endurance.

It is hoped that with a more informed understanding of the research behind the core, profession- als can eliminate confusion over its defi- nition, varied terminology, and func- tional progressive applications, and will be able to coordinate future research en- deavors. The main conclusion with the
Many randomized clinical trials have found spinal manipulation to be more effective than pla- cebo or other interventions for patients with LBP.7,25,34,114,125

Conversely, other studies have shown that manipulation is not more effective than other treat- ments.24,55,56 The incongruous results of previous trials have led some to suggest that manipulation may be effective, but only for a subgroup of patients with LBP.6

Further consideration of recent evidence for examination and intervention proce- dures may help to clarify procedures to identify and manage patients in a ma- nipulation subgroup.

Examination Considerations
Traditionally, classifying a patient as needing manipulation has relied heavily on mobility assessments and special tests
based in biomechanical theories, and the examination procedures related to these theories were originally advocated as important classification criteria (TABLE 1). Many of these diagnostic tests have been found to have poor reliability and questionable validity38,39,41 and therefore no longer appear to be the preferred method for identifying patients need- ing manipulation.

Recent research has focused on identifying baseline exami- nation factors that are associated with benefiting from manipulation interven- tions without assumptions based on theory or tradition.

Studies examining predictors of response to chiropractic treatment using manipulation have re- ported that patients with shorter dura- tion of symptoms and the absence of leg pain are most likely to benefit.8,110

We have pursued the development of a multivariate clinical prediction rule (CPR) to accurately identify patients who fit a manipulation classification.

A CPR is a tool designed to assist the classification process and improve decision making by using evidence to determine which pa- tients are likely to benefit from a specific treatment strategy.81 The goal of the CPR for the manipulation classification is to identify patients with LBP who are likely to respond to manipulation with rapid and sustained improvement.

Flynn et al41 developed a CPR for the manipula- tion classification by examining predic- tors of improvement defined as a 50% or greater reduction in self-reported disabil- ity occurring over 2 treatment sessions in 71 patients with nonradicular LBP. The CPR included 5 factors: current sympom duration of less than 16 days, a score on the work subscale of the Fear-Avoid- ance Beliefs Questionnaire (FABQ)119 of less than 19, hypomobility of the lumbar spine as assessed with posterior-to-ante- rior pressure, internal rotation of at least 1 hip greater than 35°, and symptoms not extending distal to the knee.

When 4 of these 5 factors were present, patients were highly likely to improve (positive likelihood ratio [LR], 24), while the pres- ence of 2 or fewer factors was almost al- ways associated with a failure to improve (negative LR, 0.09). To put these results in perspective, if it is assumed that about 50% of all patients with nonradicular LBP would improve with manipulation, the likelihood of improvement would increase to 97% when at least 4 factors were present and decrease to 9% when 2 or fewer factors were present.

A follow-up study25 was carried out to examine the validity of the CPR by ran- domly assigning 131 patients to receive a standardized exercise program with or without manipulation and by examin- ing the results in subgroups of patients based on their status on the manipula- tion classification CPR.

The results dem- onstrated that patients who were positive on the CPR (ie, 4 or more factors) and re- ceived manipulation experienced greater improvement in pain and disability in short-term (at 1 and 4 weeks) and long- term (6 months) follow-ups than patients who were negative on the CPR (ie, fewer than 4 factors) and received manipulation (FIGURE 1).

Patients who were positive on the CPR and received manipulation also experienced greater short- and long-term improvements in pain and disability than patients who were positive on the CPR but received the exercise intervention. These results indicate that the subgroup of pa- tients identified by the CPR is uniquely re- sponsive to a manipulation intervention.

The criteria for identifying patients in the manipulation classification have evolved from factors based largely on biomechanical theory to factors identified through prospective analysis with com- parisons to clinical outcomes. Studies in his area appear to consistently support 2 factors (short duration of symptoms and no leg pain) as important criteria for the manipulation classification,8,41,44,110 and the presence of at least 4 of the 5 CPR factors increases accuracy of predicting success even further.

The value of a classification approach is not only the ability to identify the patients likely to benefit from a par- ticular intervention, but also the ability to identify patients who need a different approach. Patients with 2 or fewer CPR factors appear very unlikely to improve with manipulation and likely need an al- ternative intervention.

It is also important to note that patients over the age of 60 or with signs of nerve root compression were excluded from consideration in the studies developing this CPR, as were pa- tients with diagnoses of spondylolisthesis, osteoporosis, or any concerns of bony ab- normality or weakness.

Manipulation is generally considered to be contraindicat- ed in these subgroups,82,102 although some believe that manipulation may be appro- priate for at least some patients with signs of nerve root compression.19,108

Management Considerations
Biomechanical theories traditionally used to identify patients for the manipulation classification have also supported the need for precise techniques to address specific dysfunctions.57,86 The importance of the choice of a specific manipulation technique has recently been challenged as traditional theories underlying manip- ulation are questioned.26,30

Although evi- dence is sparse, a few studies have found greater benefit from thrust manipulation techniques versus nonthrust mobilization for the lumbosacral region.59,92 Although manipulation is generally recommended as superior to mobilization procedures,20 there is presently no evidence for the su- periority of one manipulation technique over another.29 It is possible that the choice of a specific manipulation tech- nique may not be as important as previ- ously thought.76

Originally the manipulation classifica- tion proposed by Delitto and colleagues35 incorporated traditional biomechanical approaches to technique selection, dis- tinguishing techniques directed towards the sacroiliac or lumbar region (TABLE 2). Recent evidence, however, suggests that the effects of manipulation may not be as specific as once believed.

For example, Beffa et al9 examined the relationship be- tween manipulation targeted to specific spinal levels and the spinal levels actu- ally producing a cavitation during the technique. The authors found no correla- tion between the spinal levels producing cavitation sounds and the levels targeted by the technique.

Haas et al58 examined short-term outcomes of patients with neck pain randomized to receive ma- nipulation targeted to spinal segments thought to have increased stiffness based on clinical examination or targeted to randomly selected segments, and found no differences in patient-reported pain or stiffness.

Kent et al76 systematically reviewed the evidence on the effect of the discretion given to clinicians to choose techniques for a particular patient on outcomes in randomized trials examining manual therapy and found that although the evidence was limited, there was no suggestion that allowing clinicians to select techniques for patients improved outcomes compared with studies using predefined manipulation protocols.76

Ac- cumulating evidence suggests that the most important factor to achieve optimal outcomes with manipulation may be the accurate identification of patients who are likely to respond rather than the se- lection of specific techniques.
The concept of a subgroup of patients with LBP related to spinal instability has been described for decades, but was initially discussed as a mechanical condition of excessive move- ment between adjacent vertebrae that required immobilization or surgical sta- bilization.52,96,109 The original classifica- tion system proposed in 199535 reflected this perspective, labeling this subgroup "immobilization" and recommending ex- amination criteria and interventions de- signed to manage patients with excessive segmental movement (TABLES 1 and 2).

Re- cent research has provided a somewhat different perspective by emphasizing the importance of spinal muscles in main- taining and restoring spinal stability, shifting the focus of rehabilitation from immobilization to stabilization.23,32,69,70

In the last few years, this research has greatly increased the popularity of exercise inter- ventions designed to enhance the stabi- lizing capacity of spinal muscles.102

There have been several randomized trials pub- lished to investigate the effectiveness of lumbar stabilization exercises for patients with LBP that have reported inconsistent results.23,56,67,80,99,109 As previously suggest- ed, these conflicting results may suggest that stabilization exercises are effective for some, but not all, patients with LBP.

Further evaluation of recent evidence on the examination and intervention proce- dures related to the subgroup of patients most likely to benefit from stabilization exercise may improve identification and management of these patients.

Examination Considerations
Delitto et al35 originally described the classification criteria for a stabilization subgroup that focused on identifying patients presumed to have excessive seg- mental movements of the spine (TABLE 1), such as recurrent LBP episodes, frequent manipulation or self-manipulation with short-term relief, trauma, pregnancy, oral contraceptive use, and positive response to immobilization of the spine. Recent surveys of physical therapists suggest that this perspective on identifying patients for stabilization interventions remains prevalent.33,75

Most research conducted to iden- tify stabilization classification criteria has examined the usefulness of clinical examination findings for identifying radiographic evidence of excessive mo- tion between vertebrae.1,40,51

However, the validity of this approach has been questioned based on studies showing wide interindividual and intraindivid ual variations in spinal motion char- acteristics in asymptomatic subjects, making it difficult to establish thresh- olds identifying a spine as unstable.14,63

Using the amount of segmental motion as the standard against which examina- tion variables are judged also fails to account for the important role of the spinal muscles,48 and it is inconsistent with the goal of a classification ap- proach. Classification seeks to identify patients likely to respond to a specific treatment approach, not those with a particular imaging finding.

We have sought to identify examina- tion criteria for the stabilization clas- sification by developing a CPR for this subgroup. Hicks et al65 provided 8 weeks of stabilization training targeting the multifidus/erector spinae, transversus abdominus, and oblique abdominal muscles to 54 patients with nonradicular LBP. Using a definition of improvement (50% reduction in self-reported dis- ability), the authors identified 4 factors that were predictive of improvement: age less than 40 years, average straight- leg raise (SLR) range of motion (ROM) greater than 91°, aberrant movements during sagittal plane lumbar ROM, and a positive prone instability test (TABLE 3).65

A preliminary CPR was defined as positive when 3 or more of these factors were present; however, the predictive ac- curacy of the stabilization CPR (positive LR, 4.0) was not as strong as the ma- nipulation CPR. Assuming that a patient has a 50% chance of improving with a stabilization intervention, a positive CPR increases the probability to 80%. Great- er accuracy was found for identifying patients who were not likely to receive even minimal benefit (5 or fewer points of improvement on the Oswestry) from a stabilization intervention.

Four factors predictive of failure included a negative prone instability test, absence of aberrant movements during sagittal plane lumbar ROM, absence of lumbar hypermobility (assessed with posterior-to-anterior pres- sure), and a score of less than 9 on the FABQ physical activity subscale.65

The presence of at least 3 of these findings was highly predictive of failure (positive LR, 18.8), indicating that if a patient was presumed to have a 25% probability of failing, the presence of at least 3 of these factors would increase the probability of failure to 86%.

Stuge and colleagues112,113 have pro- posed additional factors to identify some women with posterior pelvic girdle pain who are postpartum as likely to benefit from stabilization treatment.

The criteria used to define this subgroup are women who are postpartum with buttock pain and a composite of positive tests: poste- rior pelvic pain provocation (P4) test,97 active straight-leg raise (ASLR) test,93 provocation of the long dorsal sacroiliac ligament, provocation of the pubic sym- physis with palpation, and the modified Trendelenburg test

The variables identified in these stud- ies are generally consistent with current theories emphasizing the importance of spinal muscles as a component of stabilization.

Patients in the stabiliza- tion classification appear to be those who are generally flexible (ie, younger, excessive SLR ROM) or with increased flexibility (ie, postpartum), possibly with increased segmental spinal move- ment (ie, hypermobility), whose spinal muscles do not provide adequate stabi- lization (ie, aberrant movements, and positive prone instability, ASLR, and modified Trendelenburg tests). Further research is necessary to refine and vali- date the criteria defining the stabiliza- tion classification.

Management Considerations
The original classification system35 pro- posed interventions focused on restrict- ing movement that was presumed to be excessive for patients in a stabilization classification. Recommendations in- cluded avoiding end-range positions of the spine and bracing for more severe cases, along with spinal muscle strength- ening exercises.

Research on the stabi- lizing role of spinal muscles has shifted the focus of treatment for patients in the stabilization classification from avoiding to controlling movement. In particular, recent research has stressed the impor- tance of the deep muscles of the spine for stabilization (ie, transversus abdo- minus, multifidus).68,69,71

This research has increased attention on stabilization exercise programs that emphasize spe- cific retraining of these muscles.98,103 Others have focused stabilization exer- cise regimens on improving the strength and endurance of larger spinal muscles (ie, erector spinae, oblique abdominals, quadratus lumborum),88-90 creating some disagreement concerning optimal inter- vention strategies for patients in the sta- bilization classification.

Support for the specific-muscle ap- proach to stabilization comes from ran- domized trials that have found better outcomes resulting from stabilization exercise programs centered on retraining appropriate activation of the transversus abdominus and/or multifidus muscles when compared to no treatment,67,109 or multimodal treatment programs not explicitly focused on strengthening exercises.56,99,113

Two recent studies23,80 have ques- tioned if specific muscle retraining is the
Cairns et al23 randomized 97 patients with a prior history of LBP to specific muscle retraining or conventional physi- cal therapy.

Both groups received indi- vidually tailored exercise and manual therapy interventions. The specific mus- cle retraining group received additional instruction in retraining the multifidus and transversus abdominus, supplement- ed with written instructions and real- time ultrasound biofeedback as needed.
after 12 weeks of treatment or at 1-year follow-up.23

Koumantakis et al80 also examined patients with recurrent LBP, randomizing 67 subjects to a specific-re- training group that focused initially on retraining the multifidus and transversus abdominus or to a general-strengthening group that concentrated on strengthen- ing the large muscle groups of the spine (erector spinae, oblique abdominals). The authors found somewhat superior outcomes for the general-strengthening group following the 8-week treatment
week follow-up.80

Further research is needed to identify
for patients in the stabilization classifi- cation. Although many experts advocate the necessity of specifically retraining the deep spinal muscles,98,104 the evidence does not clearly support this approach.

It appears that specific muscle retraining protocols are superior to treatments that do not include a well-defined strength- ening component, but the superiority of a specific approach to muscle retraining over an approach that stresses general strengthening of the larger spinal mus- cles has not been demonstrated.
The existence of subgroups of patients who preferentially respond to repeated end-range movements was popularized by McKenzie several decades ago.91 Consistent with principles proposed by McKenzie, Delitto and col- leagues35 identified a classification of pa- tients for whom repeated exercises in a specific direction (flexion, extension, or a lateral shift) were proposed to be the ap- propriate intervention.

The presence of the centralization phenomenon was the primary examination criterion proposed for membership in a specific-exercise classification, and the movement produc- ing centralization determined the specific direction of exercise required for the pa- tient.

The first generation of randomized trials examining specific-exercise inter- ventions found no evidence of benefit in heterogeneous samples of patients with LBP,24,36,72,87 leading to conclusions that specific-exercise protocols were no bet- ter than nonspecific approaches, or no treatment at all.116

Supporting evidence is sparse, but is beginning to emerge in support of the belief that some pa- tients respond best to specific-exercise interventions.21,85

Examination Considerations

The centralization phenomenon has traditionally been considered the hall- mark examination criterion identifying a patient for specific-exercise classifica- tion.91

Although proposed definitions vary slightly,3 centralization is defined in the classification system as occurring when a movement or position results in abolishment of pain or paresthesia, or causes migration of symptoms from an area more distal or lateral in the buttocks and/or lower extremity to a location more proximal or closer to the midline of the lumbar spine.

Several authors have found that patients who exhibit central- ization during active movement testing have a better prognosis than those with- out centralization53,74,84,111,120; however,
most studies have not used centralization to identify a specific subgroup of patients who preferentially respond to specific- exercise interventions. A recent study21 used centralization as an inclusion cri- terion and examined the effectiveness of an extension specific-exercise protocol compared to a stabilization approach.

The results showed better outcomes in the group receiving the extension proto- col in this sample of patients who dem- onstrated centralization with extension movements at baseline.21 This is the first study to provide some evidence of the usefulness of centralization as a clas- sification criterion for specific-exercise classifications.

An examination finding related to cen- tralization that has also been studied as a classification criterion for specific exer- cise is the finding of a directional prefer- ence. A directional preference is defined as a situation in which movement in one direction improves pain and limitation of ROM, and movement in the opposite direction causes signs and symptoms to worsen.77

A patient who exhibits central- ization with a movement would be con- sidered to have a directional preference for that movement; but centralization is not required, making directional prefer- ence a broader category of patients. Long et al83 studied patients with a directional preference, randomizing them to receive a specific-exercise intervention in the direction that matched their directional preference, a specific-exercise interven- tion in an unmatched direction, or a con- trol group.

The results indicated greater reductions in disability over a 2-week follow-up period when the specific-exer- cise regimen was matched to the patient's directional preference as compared to the group receiving the unmatched-ex- ercise direction.83

Additional research is needed to examine the usefulness of centralization and directional preference for identifying patients likely to respond to specific-exercise interventions. Future research may also identify additional ex- amination criteria for specific-exercise classifications.

Management Considerations

The basic premise advocated for treating patients in a specific-exercise classification is to use repeated end-range movements in the direction that caused centraliza- tion. This approach was recommended in the original classification system,35 leading to 3 categories based on the cen- tralizing movement (flexion, extension, or a lateral shift).

Two recent systematic reviews27,85 have pooled data from 6 ran- domized or quasi-experimental studies investigating the effects of treatment pro- vided according to principles proposed by McKenzie, a large component of which is repeated end-range movement in the di- rection of centralization.91

These reviews found greater reductions in pain and dis- ability for treatments based on McKen- zie principles in the short term, but the differences were small in magnitude and no longer significant at long-term follow- up.27,85

Studies included in these reviews used broad inclusion criteria, which may explain the small treatment effects. The reviews also included only studies with treatments provided according to McK- enzie principles. Examining a broader group of studies may provide additional insight into the management of specific- exercise classifications.

The most common direction used with patients in a specific-exercise classi- fication is extension,50 and extension pro- tocols have been studied the most. The study by Long et al83 included 230 pa- tients with LBP and/or sciatica who had a directional preference, and randomly as- signed them to receive exercises matching their preference, exercises opposite the identified preference, or a control group.

For 83% of the patients extension was the direction of preference. The matched-di- rection treatment protocol in this study included 2 components: repeated end- range exercises (eg, prone press-ups) and patient education.

Although patients with an extension preference were not considered separately, the predominance of an extension preference makes it likely that the matched direction treatment was more effective for the subgroup. Petersen et al109 studied 260 patients with chronic LBP with or without sciatica, comparing an extension-oriented protocol with a general-strengthening program.

In this study the extension protocol included repeated end-range extension exercise along with mobilization performed by a physical therapist. Although the sample was heterogeneous, short-term results favored the extension protocol group, but the treatment effects were small.100

Browder et al,21 in a sample of patients who centralized with extension, also found better results for a group receiv- ing mobilization (graded mobilization to promote extension) along with extension exercises and patient education.

The op- timal intervention strategy for patients in the extension specific-exercise classifi- cation may be a combination of exercise and mobilization to promote end-range extension.

Flexion specific-exercise classification appears to be less common83 and most likely occurs in patients who are older, often with a medical diagnosis of lumbar spinal stenosis.47

Interventions originally advocated for patients in the flexion spe- cific-exercise classification were flexion- oriented exercises (eg, knee-to-chest, pelvic tilts, etc), and traction with the pa- tient in a position of spinal flexion if there was a diagnosis of lumbar spinal steno- sis.35 Little research has been performed examining the effectiveness of interven- tion strategies for these patients, and most research has focused on patients with stenosis instead of a more general flexion specific-exercise classification.

Case studies of patients with stenosis have advocated intervention strategies, including mobilization or manipulation for the lumbar spine and/or hip, general lower extremity strengthening, neural mobilizations, and a walking program possibly facilitated with body weight- supported treadmill ambulation.49,95,123

A recent randomized trial122 examined patients over age 50 with a directional preference for flexion and imaging evi- dence of lumbar spinal stenosis. One group received manual therapy (mobilization or manipulation of the spine and/ or lower extremity), exercise to address impairments of strength or flexibility, and a body weight-supported treadmill-walk- ing program.

The other group received flexion-oriented exercises, a treadmill- walking program (without body weight support), and subtherapeutic ultrasound. Better outcomes were reported by the group receiving manual therapy, exercise, and body weight-supported walking.122

The multimodal intervention protocol precludes conclusions on any individual procedure; however, the results suggest that interventions for patients in the flex- ion specific-exercise classification should include several components other than flexion-oriented exercise.
The third movement direction in the specific-exercise classification is a lateral shift, which is considerably less common than flexion or extension categories.50,83

For example, only 7% of the subjects with a directional preference studied by Long et al83 had a preference for a lateral shift movement. In the original classifi- cation system, treatment for patients in the lateral shift specific-exercise clas- sification included repeated end-range lateral-shifting exercise or traction (me- chanical or autotraction).35,42

Harrison et al60 reported the results of a nonran- domized comparison of patients with a visible lateral shift who received a pro- gram of repeated lateral-shift exercises and mechanical traction, and reported greater pain reductions and correction of the shift, compared to a group of pa- tients receiving no treatment.

Gillan et al54 studied 40 patients with a visible lateral shift, randomizing patients to management with repeated end-range lateral-shift exercises or nonspecific ad- vice and massage.

The group receiving the lateral-shift exercises experienced more rapid resolution of the lateral shift, but no differences were found in disabil- ity outcomes after 3 months.54 Further research is required to clarify the most effective intervention strategies for pa- tients in the lateral-shift specific-exer- cise classification.
Although there was no evidence
to support the contention, Dellito
3 and colleagues hypothesized that
there is a subset of patients with LBP who would likely benefit from traction. The examination criteria defining this sub- group was proposed to be the presence of lower extremity symptoms and signs of nerve root compression and the absence of centralization with movement testing. There continues to be a lack of evidence supporting the use of traction for patients with LBP, and the intervention is gener- ally not recommended by systematic re- views and practice guidelines.28,78,117

Studies that have shown no benefit from using traction have not sought to identify the patients who are most likely to benefit from the intervention, but have instead used nonspecific inclusion crite- ria, essentially allowing all patients fitting a broad definition of acute or chronic LBP to enter.11,121

Recent systematic reviews on the effectiveness of traction as an inter- vention for patients with LBP,54,61 while acknowledging the lack of any evidence to support the use of traction, also note that this may be related to the fact that studies have included "mixed groups" of patients rather than homogenous sam- ples presumed to be likely to benefit from the intervention.

Similar to the recommendations of Delitto et al,35 the most common exami- nation criterion cited by clinicians as an indication for traction is the presence of signs of nerve root compression.61 Buerskens et al10 compared the effects of mechanical traction (maximum force, 35%-50% of body weight) to sham trac- tion (maximum force, 20% of body weight) for 12 sessions over 5 weeks in patients with nonspecific LBP of at least 6 weeks in duration. Following treat- ment, there was no difference between groups for perceived recovery.

The au- thors performed a secondary analysis in an attempt to identify a subgroup of patients responding positively to traction and considered the following variables: age, sex, duration of episode, radiation of symptoms below the knee, general health, severity of symptoms, maximum traction force used, and the physical therapist's belief that traction would be beneficial for the patient. None of the aforementioned subgroups were found to have experi- enced a greater benefit with mechanical traction as compared to sham traction.10

The authors did not investigate all exam- ination criteria proposed in the original classification system, and perhaps factors such as signs of nerve root compression and absence of centralization will prove to be important examination criteria for identifying a traction classification.

We believe the available research can be interpreted to indicate that the major- ity of patients with LBP are not appro- priate for a traction intervention and, therefore, traction should not be widely used for patients with LBP. It does not appear that current clinical decision making used by physical therapists is adequate for identifying which patients with LBP may respond to a traction in- tervention.10

Future research is needed to determine if examination criteria exist that can identify a patient who is likely to respond to traction. Additional research is also necessary to define the parameters that may maximize any treatment effect (eg, traction force and duration, patient position, etc).
In 1998, Riddle provided a review
and critique of classification systems
for the management of patients with LBP, including the system proposed by Delitto and colleagues22 using defined methodological guidelines. At that time, the classification system satisfied only 50% of the methodological criteria re- lated to feasibility, reliability, generaliz- ability, and content, face, and construct validity.105 The system has evolved con- siderably since 1998, and many deficient areas have been addressed through ongo- ing research.

One deficient area105 was the lack of
specific, reliable criteria for inclusion into each classification. Further research identifying examination criteria for the manipulation, stabilization, and spe- cific-exercise groups has been conducted with distinct criteria identified for each classification. Interrater reliability of the individual factors identified for the manipulation,41 stabilization,51,66 and specific-exercise46 subgroups has been published.

The reliability of classification judg- ments made using the system was also
an area of concern105 that has now been examined in several studies.

Heiss et al64 studied the reliability of the classi- fication system among 4 different raters who were inexperienced with using the system. Following a 1-day training ses- sion, the clinicians classified 45 consecu- tive patients with LBP, with each rater blind to the others' decisions. T

hree out of 4 rater pairs achieved a kappa value of 0.45 (55% agreement). This kappa value was slightly lower than that reported by Fritz and George50 (65% agreement with
a kappa value of 0.56) in a study using more experienced examiners. The clas- sification system has continued to evolve, and a recent study examined the reliabil- ity of a more explicit decision-making algorithm (FIGURE 2), with the traction classification removed and using thera- pists with varying levels of experience with the system.43 The overall agreement between therapists was 76%, with a kap- pa value of 0.60 (95% CI: 0.56, 0.64). No differences in agreement existed based on experience.43

Additional criteria for a classification system are that it should be simple, easy to understand, and indicate if special training is required.22,105 While the origi- nal algorithm for the classification system was quite complex, with multiple steps and considerations, modifications made based on emerging evidence has simpli- fied the decision-making scheme (FIG- URE 2), which appears to have improved the reliability of the system and should increase the ability to incorporate deci- sion making into clinical practice with- out specific training.

It also appears that the intervention strategies proposed by the classification system can be applied effectively by physical therapists regard- less of clinical experience. Whitman et al124 found no difference in outcomes as- sociated with therapists' years of experi- ence in a group of patients with LBP who received manipulation or stabilization exercise interventions.

While it is useful to have evidence for the validity of the specific interventions in each classification, perhaps the most important factor to consider is whether overall outcomes are improved when the system is used as compared to some al- ternative approach.22 Two randomized trials18,45 have compared use of this clas- sification system to other decision-mak- ing approaches for the management of patients with LBP in physical therapy.

Fritz et al45 randomly assigned 78 pa- tients with acute, work-related LBP to treatment based on the classification sys- tem or a current clinical practice guide- line.12 All patients attended a mean of 5 physical therapy sessions.

At the 4-week follow-up, patients treated with the clas- sification approach exhibited significant- ly greater improvement in disability and general health status, higher satisfaction, and increased likelihood of returning to work than patients treated based on the guidelines.

More recently Brennan and colleagues18 randomly assigned 123 pa- tients to receive treatment according to the stabilization, manipulation, or specif- ic-exercise classification, then compared patients matched or unmatched to their treatment group. At the 4-week and 1-year follow-ups, patients receiving matched treatment exhibited significantly greater reductions in disability than those in the unmatched-treatment group.18

Both stud- ies provide support for the classification system as a decision-making scheme to place patients with LBP into subgroups that indicate the interventions that are most likely to provide benefit.
the "core" has been used to refer to the lumbopelvic-hip complex, which involves deeper muscles, such as the internal oblique, transversus abdominis, transversospinalis (multifidus, rotatores, semispinalis), quadratus lumborum, and psoas major and minor, and superficial muscles, such as the rectus abdominis, external oblique, erector spinae (iliocostalis, spinalis, longissimus), latissimus dorsi, gluteus maximus and me- dius, hamstrings, and rectus femoris.2,24,25

Core muscle development is believed to be important in many functional and athletic activities, because core muscle recruitment should enhance core stabil- ity and help provide proximal stability to facilitate distal mobility. For optimal core stability, both the smaller, deeper core muscles and the larger, superficial core muscles must contract in sequence with appropriate timing and tension.26,27

En- hanced stability and neuromuscular con- trol of the lumbopelvic-hip complex has been shown to decrease the risk of knee injuries, especially in females.29,37 Zazulak et al37 reported that female athletes with less trunk control had a higher risk of knee injuries, especially anterior cruciate ligament injuries, compared to athletes who exhibited greater trunk control.

The use of Swiss ball training for core muscle development has been popular for several years.8 Multiple studies have examined core muscle recruitment dur- ing varying types of Swiss ball abdominal exercises8,28,35,36 and during traditional abdominal exercises like the crunch (abdominal curl-up) and bent-knee sit- up.13,14,35,36

Most researchers who studied the use of Swiss ball exercises quanti- fied abdominal muscle activity during the crunch, push-up, and bench press exercises, and typically investigated the recruitment patterns of only 1 or 2 muscles.5,15,22,23,32

Numerous other Swiss ball exercises are used in training and reha- bilitation to enhance core development and stability. For example, prone hip extension performed on a Swiss ball is commonly used for gluteus maximus and hamstrings development.

However, the extent that performing prone hip exten- sion on a Swiss ball recruits core muscles has not yet been investigated. Moreover, there are several additional higher-level Swiss ball exercises that are used by ath- letes, such as the roll-out, pike, knee-out, and skier, but their effectiveness in re- cruiting core muscles is unknown.

Many of these exercises are chosen based on functionality or sport specificity. Never- theless, it remains unclear how perform- ing traditional abdominal-strengthening exercises, such as the crunch and bent- knee sit-up, compares to performing a progression of Swiss ball exercises, with respect to core muscle recruitment.
Understanding which core muscles are recruited and how active they are while performing a variety of Swiss ball and traditional abdominal exercises is helpful to therapists and other healthcare or fitness specialists who develop specific abdominal exercises for their patients or clients to facilitate their rehabilitation or training objectives.

The purpose of this study was to test the ability of 8 Swiss ball abdominal exercises and 2 tradi- tional abdominal exercises on activating core muscles. It was hypothesized that normalized electromyographic (EMG) signals from core muscles would be sig- nificantly greater in Swiss ball exercises compared to traditional abdominal exer- cises, and would be significantly less in the sitting march right exercise compared to the remaining Swiss ball exercises.
significant differences were observed in normalized EMG data among exercises (taBle 1).

Upper rectus abdominis EMG signal was sig- nificantly greater with the roll-out com- pared to all remaining exercises except the pike and crunch, and significantly less with the sitting march right com- pared to all other exercises. Lower rectus abdominis EMG signal was significantly greater with the pike compared to all ex- ercises except the roll-out and hip exten- sion right, and significantly less with the sitting march right compared to all other exercises.

External oblique EMG signal was significantly greater with the pike, knee-up, and skier compared to the hip extension left, decline push-up, sitting march right, crunch, and bent-knee sit- up, and significantly less with the sitting march right compared to all other exer- cises except the crunch and bent-knee sit-up (additional differences among exercises are indicated in taBle 1).

The internal oblique EMG signal was signifi cantly greater with the pike compared to Graphical representations of upper rec- the hip extension right, decline push-up, tus abdominis, lower rectus abdominis, sitting march right, crunch, and bent- external oblique, and internal oblique knee sit-up, and was significantly less EMG signals, ranked from highest to with the sitting march right compared to lowest among all exercises, are shown in all exercises except the bent-knee sit-up. fiGures 14 to 17, and the relative intensities of the exercises with respect to core mus- cle recruitment are shown in taBle 2.

Lumbar paraspinal EMG signal was less than 10% MVIC, with the great- est activity noted with the pike exercise. Latissimus dorsi EMG signal was sig- nificantly greater with the pike, knee-up, skier, hip extension right, hip extension left, and decline push-up, compared to the sitting march right, crunch, and bent- knee sit-up, and significantly greater in the pike, knee-up, skier, and hip exten- sion left, compared to the roll-out. Rectus femoris EMG signal was highest with the pike, knee-up, skier, hip extension left, and bent-knee sit-up compared to the roll-out, hip extension right, and crunch (additional differences among exercises are indicated in taBle 1).

From the 15-point (6-20) Borg Scale, the mean (SD) perceived exertion from highest to lowest was 14.6 (2.1) for the pike, 13.3 (1.5) for the skier, 12.9 (1.4) for the decline push-up, 12.9 (1.8) for the hip extension exercises, 12.7 (1.5) for the knee-up, 12.6 (2.2) for the roll-out, 10.4 (2.5) bent-knee sit-up, 10.2 (2.2) for the crunch, and 9.2 (2.2) for the sit- ting march.
The relatively high core muscle activity during the pike, roll-out, knee-up, and skier exercises, compared to the crunch and bent-knee sit-up exercises, suggests that these exercises are good alternatives to traditional abdominal exercises for core muscle recruitment. Moreover, these exercises may be beneficial for individu- als with limited workout time and whose goal is to perform exercises that not only provide an abdominal workout but also an upper and lower extremity workout.

These exercises may also achieve a great- er energy expenditure compared to the traditional crunch and bent-knee sit-up because of the greater number of muscles recruited, and relatively high muscular activity, and this should be the focus of future research. In addition, tension in the latissimus dorsi and internal oblique (and presumably the transversus abdomi- nis), which all tense the thoracolumbar fascia, may enhance core stability while performing these exercises compared to performing the crunch and bent-knee sit-up.

The pike and roll-out were the most effective Swiss ball exercises in recruit- ing core musculature, but these exercises also required the greatest effort and were among the most difficult to perform among the 8 exercises. From the per- ceived exertion ratings scale,3 the mean (SD) perceived exertion of 14.6 (2.1) for the pike is classified as hard, which was the highest rating for all exercises.

In contrast, the mean (SD) perceived ex- ertions of 12.6 (2.2), 12.7 (1.5), and 13.3 (1.5), respectively, for the roll-out, knee- up, and skier exercises are classified as somewhat hard. Exercises such as the pike may be appropriate for highly fit individuals in the latter stages of a pro- gressive abdominal strengthening or re- habilitation program.

In choosing which abdominal exercise to use, it is important to consider the functionality of the exer- cises, or in the case of athletes, the sport specificity of the exercises. For example, the pike may be most appropriate for a diver who is performing the pike maneu- ver during the dive.
The crunch and bent-knee sit-up were both effective in recruiting abdominal musculature. Previous studies have shown higher external oblique activity during the bent-knee sit-up compared to the crunch.2,13,14,20 In the current study, no statistically significant difference was found for the mean (SD) external oblique activity between the bent-knee sit-up (36% [14%] MVIC) and the crunch (28% [17%] MVIC). Conversely, previ- ous studies have shown that the upper and lower rectus abdominis were more active during the crunch compared to the bent-knee sit-up.6,13,14,17

In the cur- rent study, no statistically significant dif- ference was found for upper and lower rectus abdominis activity between the crunch (53% [19%] and 39% [16%] MVIC, respectively) compared to the bent-knee sit-up (40% [13%] and 35% [14%] MVIC, respectively). Similar to previous studies, our data show that rec- tus femoris activity is statistically greater during the bent-knee sit-up compared to the crunch.2,13,14,20

Halpern and Bleck17 have demonstrat- ed that lumbar spinal flexion was only 3° during the crunch but approximately 30° during the bent-knee sit-up. In addition, the bent-knee sit-up has been shown to generate greater intradiscal pressure30; and lumbar compression2 compared to exercises similar to the crunch, largely due to increased lumbar flexion and hip flexor activity. This implies that the crunch may be a safer exercise to perform than the bent-knee sit-up for individu- als who need to minimize lumbar spinal flexion or compressive forces because of lumbar pathology.

From the perceived ratings scale,3 the mean (SD) perceived exertions of 10.2 (2.2) and 10.4 (2.5), respectively, for the crunch and bent-knee sit-up are classi- fied between very light to fairly light. This suggests that traditional abdominal exercises require lower demands of ef- fort compared to some Swiss ball exer- cises, such as the pike and knee-up, but higher than other Swiss ball exercises, such as the sitting march, which exhibit- ed a mean (SD) perceived exertion of 9.2 (2.2), which is classified as very light.
As core muscles contract, they help sta- bilize the core by compressing and stiff- ening the spine.26,27

This is important, because the osteoligamentous lumbar spine buckles under compressive loads of only 90 N (approximately 20 lb), and core muscles act as guy wires around the human spine to stabilize the spine and prevent spinal buckling.26,27

This il- lustrates the importance of core muscle strengthening, which has been shown to decrease injury risk and enhance perfor- mance.2,18,29 Moreover, strong abdominal muscles help stabilize the trunk and un- load the lumbar spine.2

For optimal core stability to occur, it appears that numerous core muscles, in- cluding both smaller, deeper core muscles (eg, transversospinalis, such as the mul- tifidus, as well as transversus abdominis, internal oblique, and quadratus lumbo- rum) and larger superficial core muscles (eg, erector spinae, external oblique, rectus abdominis), must contract in se- quence with appropriate timing and ten- sion.26,27

Cholewicki and VanVliet,7 who investigated the relative contribution of core muscles to lumbar spine stability, reported that no single core muscle can be identified as most important for lum- bar spine stability. Moreover, the rela- tive contribution of each core muscle to lumbar spine stability depends on trunk loading direction and magnitude (spi- nal instability is greatest during trunk flexion, such as during the bent-knee sit-up), and no one muscle contributes more than 30% to overall spine stability.7

Therefore, trunk stabilization exercises may be most effective when they involve the entire spinal musculature and its cor- responding motor control under various spine loading conditions.7 However, it should be emphasized that exercises that demand high core muscle activity not only enhance core stability but also gen- erate higher spinal compressive loading,21 which may have adverse effects in indi- viduals with lumbar spine pathology.
Understanding biomechanical differ- ences between exercises is important, because trunk flexion may be contrain- dicated in certain populations.

For ex- ample, maintaining a neutral pelvis and spine (eg, decline push-up and hip exten- sion exercises), rather than forceful flex- ion of the lumbar spine (eg, bent-knee sit-up), may be more desirable for indi- viduals with lumbar disk pathologies or osteoporosis.

With forceful lumbar spine flexion, intradiscal pressure can increase several times above normal intradiscal pressure from a resting supine position.30 In contrast, individuals with facet joint pain, spondylolisthesis, and vertebral or intervertebral foramen stenosis may bet- ter benefit from exercises that incorpo- rate some amount of trunk flexion, while minimizing trunk extension.

The role of deeper abdominal muscles
(eg, transversus abdominis and internal oblique) in enhancing spinal and pelvic stabilization and increasing intra-ab- dominal pressure has been well studied but still remains controversial.9,10

Some studies have suggested that the transver- sus abdominis is important in enhancing spinal stabilization,19,33 but other studies have questioned the importance of this muscle as a major spinal stabilizer.1,26,27 Isolated contractions from the transver- sus abdominis have not been demon- strated during functional higher-demand activities (such as those that occur during sports) that require all abdominal mus- cles to become active.16 Intra-abdominal pressure has been shown to unload the spine by generating a trunk extensor mo- ment and tensile loading to the spine.9,10

By the trunk becoming a more solid cyl- inder by the intra-abdominal pressure mechanism, there is a reduction in spinal axial compression and shear loads. The attachments of the transversus abdominis and internal oblique into the thoracolum- bar fascia may enhance spinal and pelvic stabilization, because when these muscles contract they tense the thoracolumbar fascia.

The transversus abdominis has been shown to exhibit a similar (within 15%) muscle activation pattern and am- plitude as the internal oblique during abdominal exercises performed similarly to those in the current study.20,24 The highest activity from the internal oblique occurred during the pike, roll-out, knee- up, skier, and hip extension left, which implies that these exercises may also be effective in recruiting the transversus abdominis, although future studies are needed to test this hypothesis.

Therefore, exercises such as the pike, knee-up, and roll-out may offer more effective stabili- zation to the spine and pelvis compared to exercises that recruit lower levels of in- ternal oblique and transversus abdominis activity, such as the sitting march, bent- knee sit-up, and crunch.
Performing exercises that require high activity from the hip flexors and lumbar paraspinals may not be desirable for those with weak abdominal muscles or lumbar instability, because the forces generated from these muscles tend to an- teriorly rotate the pelvis and may increase lordosis in the lumbar spine. In exercises performed similarly to those in the cur- rent study, psoas and iliacus EMG signals have been shown to be of similar magni- tudes (within 10%) and recruitment pat- terns as rectus femoris activity.24

It has also been demonstrated that the psoas muscle generates considerable spinal compression and anterior shear forces at L5-S1.20,34 Shear force may be prob- lematic for individuals with lumbar disk pathologies. Individuals with weak rec- tus abdominis and external and internal oblique musculature or lumbar instability may want to avoid the bent-knee sit-up, skier, knee-up, pike, sitting march, and hip extension exercises, due to moderate levels of hip flexor activity. In contrast, more appropriate exercises include the roll-out, decline push-up, and crunch, which all generated relatively low rectus femoris and lumbar paraspinal activities and relatively high rectus abdominis and external and internal oblique activity.

Cocontraction of the lumbar paraspi- nal muscles with rectus abdominis, external and internal oblique, and latis- simus dorsi musculature may enhance trunk stability and spine stiffness.

Al- though excessive activity from the lumbar paraspinals can cause high compressive and shear (especially L5-S1) forces on the lumbar spine,20,34 the relatively low lum- bar paraspinal activity in all 10 exercises (10% MVIC) is likely not high enough to cause deleterious effects to the healthy or pathologic lumbar spine.
Cross talk was minimized by using stan- dardized electrode positions that have been tested previously.4,31 This is espe- cially of concern for the internal oblique, which was the only muscle tested that was not superficial. Because the internal oblique is deep to the external oblique, it is potentially susceptible to considerable EMG cross talk from the external oblique. However, surface EMG electrodes are considered appropriate for monitor- ing the internal oblique when they are located within the triangle confined by the inguinal ligament, lateral border of the rectus sheath, and a line connecting the ASISs, and especially when clini- cal questions are being discussed and a small percentage of EMG cross talk is acceptable. In fact, when performing ab- dominal exercises similar to the exercises in the current study, mean internal and external oblique EMG data from surface electrodes (similarly located as in the current study) were only approximately 10% different compared to mean inter- nal and external oblique EMG data from intramuscular electrodes.24 McGill et al24 have concluded that appropriately placed surface electrodes accurately reflect (wi- thin 10%) the muscle activity within the internal or external oblique muscles.

Another limitation from the current study is being able to interpret how the EMG signal is related to muscle force. The clinician should be cautious when relating the EMG amplitude with mus- cle force and strength during dynamic exercises, as eccentric muscle actions can result in lower activity but higher force, while concentric muscle actions can result in higher muscle activity but lower force.20,34

Linear, quasi-linear (near linear), and nonlinear correlations have been reported in the literature be- tween EMG amplitude and muscle force (strength) during isometric muscle ac- tions.20,34

Generally, the relationship be- tween EMG amplitude and muscle force is most linear during isometric muscle actions or during activities when muscle length is not changing rapidly during concentric and eccentric muscle actions, which occurred while performing the ex- ercises in the current study.

In contrast, the relationship between EMG amplitude and muscle force is most often nonlinear during activities in which muscles change length rapidly or during muscle fatigue, which did not occur in the current study.
Key Points
finDinGs: Swiss ball exercises provided
a wide range of activation of the core musculature.
imPliCation: Our findings can be used
to help guide core stability training and rehabilitation, using a variety of Swiss ball and traditional abdominal exercises. Caution: The clinician should be cau- tious when relating the EMG amplitude with muscle force and strength during dynamic exercises.
ACKNOWLEDGEMENTS: We would like to ac- knowledge the graduate students in the De- partment of Physical Therapy at California State University, Sacramento, for all their as- sistance in data collection for this project.
1. Allison GT, Morris SL, Lay B. Feedforward responses of transversus abdominis are di- rectionally specific and act asymmetrically: implications for core stability theories. J Orthop Sports Phys Ther. 2008;38:228-237. http://
2. Axler CT, McGill SM. Low back loads over a variety of abdominal exercises: searching for the safest abdominal challenge. Med Sci Sports Exerc. 1997;29:804-811.
3. Balady G, Berra K, La G. Physical fitness test- ing and interpretation. In: American College of Sports Medicine. ACSM's Guidelines for Exercise Testing and Prescription. Baltimore, MD: Lippin- cott, Williams and Wilkins; 2000.
4. Basmajian JV, Blumenstein R. Electrode Place- ment in EMG Biofeedback. Baltimore, MD:

Wil- liams and Wilkins; 1980.
wiss ball exercises employed in
a prone position were as effective
or more effective in generating core muscle activity compared to the tradi- tional crunch and bent-knee sit-up. The roll-out and pike were the most effective exercises in activating the core mus- cles compared to all exercises. Lumbar paraspinal activity was relatively low for all exercises. The sitting march exercise generated the lowest core mtuscle activity compared to all exercises.
Fortheorthopedist,thepatientpresentingwithlowbackpainis often approached apprehensively. Within the general population, the prevalence of low back pain ranks second only to the common cold as a cause of all physician visits.4 The ubiquitous nature of this complaint canarisefrommultiplecausesthatcanmakeattainingpositivetreatment outcomes very difficult.

However, in the pediatric and adolescent athletic population, any complaint of low back pain must be taken seriously and assumed to be a significant problem until proved otherwise.17, 19 Back injuriesandbackpainintheyoungathleteoccurin10%to15%of participants, with up to 75% of high performance athletes having had back pain.9, 15, 22

This prevalence does vary between sports and positions played.28 A full and comprehensive evaluation is usually recommended foranyathletewithlowbackpainrenderinghimorherunableto participateorcontinuingformorethan10days.39

Accurate diagnosis of back pain in the young athlete requires a complete and thorough history and physical examination of the patient.

The treatingphysicianmustbeawarethatinjuriesoccurringintheadolescentaredifferentfromthoseoccurringinadults.10Intheadult, 48% of patients with low back pain had discogenic etiologies, whereas 47% of low back pain in adolescents was from spondylolysis and 25% from hyperlordosis.25

Knowledge of this statistical data facilitates accu- rate diagnosis and thereby promotes prompt treatment in this popula- tion.

The purpose of this article is to identify the likely causes of back pain in the young athlete and provide an overview on diagnosis and
Spondylolysis represents a pars interarticularis defect frequently causingmechanicallowbackpain.Intheathleticpopulation,themajor- ity of spondylolytic lesions are related to pars interarticularis stress fracture.43 Risk factors include positive family history,14 indigenous Alaskan ancestry,35 and coincident spinal anomalies.26 Repetitive hyperexten- sion has routinely been shown to be a major risk factor particularly in gymnastics, the football lineman, figure skating, and dance.2, 16, 22-24

The patient generally complains of low-grade back pain with inter- mittent episodes of increased severity. This pain is exacerbated by hyper- extension activities such as the back walkover in gymnastics or the blockingbyoffensivelinemen.Rarelyarethereconcomitantneurologic symptoms.Symptomstendtoimproveorresolvebyavoidinghyperex- tension activities and with rest.

Physical examination reveals normal gait. There is rarely tenderness to palpation. Forward flexion is full, but pain on hyperextension is common. If pain exists, the provocative hyperextension test will demon- strate reproducible symptoms. Generally, the neurologic exam will be normal.

Often the patient will have tight hamstrings.
Completionoftheevaluationincludesstandinglumbosacralradio- graphswithobliqueviewslookingfortheso-calledScottydoglesion.If radiographs are nondiagnostic, a bone scan may demonstrate an increased uptake in the pairs indicatingastressreaction.SPECTisuseful in the absence of radiographic and scintigraphic findings. SPECT has been shown to be the most sensitive method of diagnosing spondylo- lysis.1

Treatment for symptomatic patients includes activity modification and rest. As pain diminishes, strengthening exercises targeting the bac andabdominalmusculaturearerecommended.Inthesettingofacute spondylysis, immobilization in a thoracolumbosacral orthosis is indi- cated.

Nearlya75%healingrateofearlydefectshasbeenshownwith the use of orthotic device only.27 For persistently symptomatic spondy- lytic defects, open reduction internal fixation (ORIF) and bone grafting across the defect may be indicated.
Spondylolisthesisintheyoungathleteisusuallyassociatedwith either a pars interarticularis defect or elongation.2, 42 Most of the slip progression occurs during the preadolescent growth spurt.43

Thepatientmaypresentcomplainingoflowbackpainoraltered gait and postural abnormalities depending on the level of the slip. Diagnostic focus again should include risk factors similar to spondylo- lysis.
Physical examination may show a characteristic stiff-legged, short stride gait.

This so-called pelvic waddle is caused by tight hamstrings.31 If the slip is severe, a step-off may be appreciated at the lumbosacral junction. The buttocks may have a heart-shaped configuration secondary to the vertical position of the sacrum.

Radiographs including a spot lateral of the lumbosacral junction allow for determination of the slip percentage and slip angle. Based on the slip percentage, treatment can be instituted.

For the symptomatic athlete with slips ranging from 25% to 50%, treatment includes observation followed closely with spot lateral radio- graphs. Slippage is associated with rapid growth and with slip angles of more than 50 degrees.26 Therefore, observation must continue to the end of growth.

The patient and family must be cautioned that participa- tion in contact sports may have to be restricted if progression occurs.11 If progression occurs, pain persists, neurologic deficits develop, or the spondylolysthesis is more than 50%, posterolateral in situ fusion is the treatment of choice. After successful fusion, pain, gait abnormalities, and tight hamstrings resolve in 90% of patients.12

Controversy remains regarding techniques for reduction with instrumentation of high-grade spondylolisthesis. Postoperative neurologic deficits after reduction and/ or instrumentation have been shown to be a very infrequent occurrence.2
Sheuermann's kyphosis is thoracic kyphosis with anterior wedging of at least 5 degrees of three consecutive vertebra. There are also typical vertebral end plate changes, Schmorl's nodes, and apophyseal ring frac- tures. An increased prevalence is associated with sports such as water skiing, particularly if started before age six.38

The patient presents complaining of back pain aggrevated by pro- longed sitting, standing, or activity. Typically, there is no traumatic event leadingtothedevelopmentofpain.Examinationrevealsaroundback posture with possibly a gibbus deformity worsened with forward flexion.Thekyphosdoesnotresolvewithhyperextensionorlyingsu- pine. Radiographs are diagnostic. Treatment includes upper trunk and postural exercises.

If the kyphosis is greater than 60 degrees, thoracolum- bosacral is indicated. Surgical treatment with anterior discectomy and fusion of the apical segment along with posterior fusion of the entire kyphotic segment may be indicated with a kyphos of more than 75 degrees or a rigid curve with marked anterior wedging.

Atypical Sheuermann's kyphosis involves the area of the thoraco- lumbar junction. End-plate changes, Schmorl's nodes, and apophyseal ringfracturesmayoccur,butfrequentlyinvolveonlyonevertebra.This is frequently seen in sports with repetitive flexion and extension such as gymnastics and wrestling.36, 39

The patient again presents with low back pain exacerbated with forward flexion. Examination may show a flat thoracic spine with a tight thoracolumbar fascia. Occasionally, a palpable bump or gibbus may be felt at the affected level.39 Radiographs again may be diagnostic. A SPECT scan will show increased activity at one or twolevels.

Treatmentaddressesstretchingthetightthoracolumbarfas- cia, abdominal strengthening, and rest from athletics. A hyperextension lordoticbraceisusefulinreturningtheathletebacktosportsin1to2 months.14
Unlike adults, acute HNP in the adolescent or child is quite uncom- mon. Nevertheless, 10% of back pain in the adolescent athlete arises from a discogenic etiology.25 Athletes at risk are weight lifters and thoseparticipatingincollisionsports.9

Thepatientoftenpresentslacking sciatica because the herniation tends to be more central and the volume of extruded annulus is less than that for adults. Rather, the patient complains of low back, buttock, or posterior thigh pain. The pain is exacerbated by sitting, sports activities, coughing, or sneezing. The acute onset of symptoms is precipitated by a traumatic event in more than half of the cases.6, 7

Examination may reveal an abnormal gait secondary to paraspinal muscle spasm. There may be decreased lumbar motion. Tension signs includingthestraight-legraiseorfemoralstretchtestmaybepresentin 80% to 90% of patients.11

Neurologic findings have been reported in fewer than 40% of adolescents with HNP, most commonly extensor hallucis longus weakness or decreased reflexes.6 Plain radiographs are often normal but should be obtained to rule out other pathology. Occa- sionally, a transitional vertebra at L5 or S1 may be identified and is considered to be associated with the development of HNP.11 An MRI is

A multidisciplinary approach to treatment exists for disk herniation intheyoungathlete.

TheseincludeNSAIDs,short-termbedrest,and physical therapy exercises. Rigid bracing in months is typically required to prevent recurrence and allow healing.10 Rarely epidural steroid injections may be required. The patient may return to sports when he or she has attained full range of motion and strength. Persistent symptoms, cauda equina syndrome, progressive neurologic deficit, or reinjury are indications for discectomy. Excellent to good results in more than 90% of patients undergoing discectomy have been reported.6hyperlordosis for 3 to 4
Unique to the adolescent patient population are apophyseal ring fractures. These occur at the junction between the vertebral body and the apophysis attached to the outer annulus fibrosus before they com- pletely fuse at approximately age 18 years old. Injury to the apophyseal ringproducesavulsionsdisplacedposteriorlyintothecanalattachedto the intervertebral disc.

This produces signs and symptoms similar to a central HNP. Approximately 50% of these injuries occur secondary to acute trauma, and repetitive microtrauma accounts for another signifi- cantnumberofapophysealringfractures.35Mostpatientsareinvolved in sports such as weight lifting or that require repetitive hyperflexion of the lumbar spine.8, 21 The inferior apophysis of L4 is most commonly involved.37

The patient usually presents with complaints similar to those seen with HNP: back, buttock, and posterior thigh pain. Sciatica may or may not be present. Symptoms are worsened with prolonged sitting, coughing, sneezing, and sports activities.

Neurologic symptoms are rare. On examination, lumbar tenderness and paraspinal muscle spasm may be found. Other physical findings are similar to those with HNP. How- ever,inthepatientwithanapophysealringfracture,contralateral straight leg raise test is more frequently positive than in the patient with a herniated disc.13

Lateral radiographs may show a small avulsion fracture off of the vertebral body. CT is the imaging study of choice because MRI does not distinguish between bone and disc material well.
Treatmentforanapophysealringfracturewithoutneurologicdefi- cits is similar to that of a herniated disc.

Nonoperative treatment with rest,NSAIDs,physicaltherapy,andbracingisusuallysuccessful.If progressive neurologic deficits, cauda equina syndrome, or persistent symptoms exist, surgical excision of the bony fragment and disc material is indicated.
Discitis and vertebral osteomyelitis represent a spectrum of the same disease process. This is usually a bacterial infection secondary to hematogenous seeding owing to the unique blood supply of the pediatric spine. The blood supply traverses the vertebral endplate from body todiscestablishingaroutefortransmissionofinfection.

The patient usually presents with complaints of back pain, irritabil- ity, and other constitutional symptoms. If the infection involves the T8-L1levels,abdominalpainmaybethepresentingcomplaint.11On examination, the patient may be febrile.

The patient may appear toxic and irritable. There may be tenderness to palpation of the spine with loss of lumbar lordosis and hamstring tightness. Tension signs may be positive.
Laboratory evaluation should include a complete blood cell count with differential, erythrocyte sedimentation rate (ESR), C-reactive pro- tein (CRP), and blood cultures.

Although the ESR is usually elevated in 90% of cases, the white blood cell count may only be abnormal in 10% of cases.32 Blood cultures are only positive in 50% of the cases for the causativeorganism,withStaphylococcusaureusbeingthemostcommon.41

Radiographs of the spine may be negative if symptoms have only persisted for 2 to 3 weeks. When radiographic abnormalities exist, they include erosion and sclerosis of the end plate with a decrease in disc space height.

If radiographs are normal in the presence of abnormal laboratory results, a bone scan or MRI is indicated. MRI allows for differentiatingbetweendiscitisorvertebralosteomyelitisandanepi- dural abscess.

Treatment of discitis and vertebral osteomyelitis is usually nonoper- ative.Immobilizationalongwith1weekofparenteralantibioticsfol- lowed by 4 to 6 weeks of oral antibiotics provides symptomatic relief in 85% of patients by 2 to 3 weeks.32 Traditionally, antibiotics are continued until the ESR is normalized.
Neoplastic processes in the spine must always be considered in the differential diagnosis of a young athlete presenting with back pain.

These are exceedingly rare with only 0.5% of primary musculoskeletal tumorsoccurringinspineofachildoradolescent.5Mostoftheneo- plasms are benign and may involve the anterior or posterior elements. The most common benign neoplasms are osteiod osteoma, osteo- blastoma, and anuerysmal bone cysts.5 Primary malignant spinal neo- plasms are quite rare. These include osteosarcoma and Ewing's Sarcoma.

Leukemiaandlymphomahavealsobeenreportedintheyoungathlete.3, 33 Skeletal metastasis generally affects children under the age of 10.11 The most prevalent malignancy with spinal metastasis is neuroblastoma, particularly with a predilection for the thoracic spine.20

The patient commonly presents with a complaint of back pain both with activity and rest. Night pain, constitutional symptoms, and an atraumatic etiology of pain should alert the physician to a possible neoplastic source. Occasionally, pain will be relieved with NSAIDs. The patient or family may notice abnormalities in gait or assymetry. Rarely, neurologic symptoms caused by compression from the lesions will exist.

Examination may include the presence of a nonstructural scoliosis withparaspinalmusclespasmandtenderness.Hamstringtightnessmay be present, although focal neurologic deficits are rare. A soft-tissue mass
may be palpated posteriorly.
Imaging studies must always include plain radiographs.

graphic changes suspicious for a malignant process include thinning and destruction of pedicles, vertebral body collapse, and expansile le- sions with a soft-tissue mass. Based on history, examination, and plain films, further imaging may include bone scan, CT, or MRI.

Treatment for benign primary spinal lesions include rest, bracing, and resection. Although osteiod osteoma lesions have been reported to be self-limiting, excision of the nidus is the treatment of choice.11 This

mayincludeusingpreoperativeradioactivetracertoassistinlocalization of the mass and to ensure complete excision. If the surgeon suspects a malignant primary neoplasm, the patient should be referred to an ortho- pedic tumor specialist expeditiously for appropriate staging and treat- ment.
Back pain in the adolescent athlete serious enough to warrant medi- cal attention mandates a careful evaluation.

As discussed above, a thor- ough history and physical examination are essential. The most typical patient presentation scenario is often that of a 10- to 14-year-old girl with a new-onset back pain related to sports or activity, classically a gymnast.

The frequency of participation in practice or competition will suggest whether the symptoms are secondary to a chronic repetitive over-use syndrome or strain related to a relatively new onset activity.

One approach to managing these patients would be to first recom- mend the activity stop for a minimum of 5 to 7 days with a goal of pain relief. Imaging studies would not usually be obtained at the time of initial presentation unless indicated by specific findings. The use of NSAIDS is recommended to decrease pain. After approximately 5 days of rest, if the pain is substantially better, resumption of light activities suchasexercisesandswimmingorbikingisallowed.

NSAIDsare continued as needed, and light sport-specific activities are resumed in a 10 to 14 day period if pain is minimal or absent. If symptoms recur, activity is restricted, and this cycle is followed at a slower pace. Often, this process of rehabilitation is facilitated and guided by a physical therapist with familiarity of the sport involved. Input obtained from the therapist is helpful for determination of readiness to return to full activ- ity.

Sometimes the most difficult issue in managing back pain in the adolescent athlete is the often unrealistic expectations of the parents regarding the child's athletic ability and future prospects. The parents' attitudes are driven by the potentially huge sums of money represented by a four-year college scholarship or even the prospect of participation at the professional level.

In the author's experience, this attitude is particularlyprevalentamongparentsofgymnasts,asportinwhichthe coaches themselves have a predisposition for intensive or excessive trainingintheseyoungathletes.Usuallyaveryfrankdiscussionabout the potential risks of further injury from continued participation of an injured athlete is persuasive enough for the parent to permit some time for rest and appropriate rehabilitation. As the adolescent athlete with back pain returns to sport-related activities, a program of graduated performance and/or modifications in the training regimen agreed to by thecoachareofteninvaluableinasuccessfulandlastingresumptionof thesportsactivity.

Forexample,nothavingtheathletedoaspecific routine or exercise that may risk re-injury as a routine part of training may also be a helpful way to keep the athlete active. In gymnastics, avoidance of the back-walk-over routine would minimize hyperexten- sion stress on the lower back and thus the possibility of a recurrence on pain in this vulnerable area.

In a scenario of persistent pain after a period of rest and rehab as thepatientreturnstoactivityorevenpreventingreturntosports,work- up with imaging studies is warranted. Plain radiographs including ante- rior-posterior and lateral of the lumbosacral spine are obtained in the patienttoruleoutanobviousabnormalitylikeapre-existingspondylo- lysis of spondylolisthesis.

Should these be normal, a Technitium bone scan with SPECT imaging is indicated to assess for an early but other- wise occult spondylolysis, so common as a cause of back pain in young athletes, especially gymnasts.

Even with the finding of a positive scan and an acute spondylolysis, appropriate management of the adolescent gymnast with bracing and rest, rehabilitation, and a modified training regimen can still be a successful way to return the patient back to gymnastics.
Patients suffering from spine pain can present with a wide spectrum of symptoms and examination findings, representing different degrees of clinical severity and pathological significance. Serious etiologies of spine pain that include fractures, tumors, or infections are relatively rare, accounting for less than 1% of all med- ical cases seen during spine assessment.1

However, because most spine pain patients present with a clinical picture that could be created by numerous different conditions,1,2 it is imperative for clinicians to identify conditions or comorbidities that may deter a patient's recovery and function or place the patient at risk for serious medical consequences. A clinician must remain alert to potential clinical indicators that require more extensive testing than that afforded by a basic clinical examination.3

Comorbidities that could either deter a patient's recovery and function or place the patient at risk for serious medical consequences are often labeled as "red flags." Essentially, red flags are signs and symptoms found in the patient history and clinical examination that may tie a disorder to a serious pathology.4

eral, red flags may warrant further diagnostic workup and potentially immediate treatment by a specialist.5
Clinical screening requires the clinician to dichoto- mously rule in or rule out the presence of red flags prior to treatment (Figure 1). Ruling in or ruling out requires tests and measures that demonstrate the ability to unravel difficult signs and symptoms6 and to dis- criminate a subgroup of homogeneous characteristics from a heterogeneous pool of patients with dysfunc- tion.7

Generally, tests and measures used during clinical screening are performed at the beginning of the clinical examination as preliminary tests.8 Screening tests are designed to assist the clinician in ruling out selected diagnoses or impairments and should demonstrate high sensitivity.9,10

When a test demonstrates high sensitivity, the likelihood of a false negative is low as the test demonstrates the ability to identify accurately those who truly have the disease or impairment, thus demon- strating the ability to rule out a condition.9 Conversely, tests with high specificity are designed to correctly identify those who do not exhibit the disorder.

As these tests are more appropriate for ruling in a disorder, tests with high specificity are not typically used as screening tools.9,10

Despite the importance of assessing red flags, recent evidence suggests they are not routinely used. For exam- ple, less than 5% of primary care physicians routinely examine for red flags during their initial screen.11

Even when provided with guidelines for examination and management of patients with acute back pain, clinicians demonstrate poor concordance with examination using guideline-recommended approaches.12,13

In a review of six different international guidelines for management of spine pain, all guidelines recommended a specific screen for detection of red flags.14 Although the six interna- tional guidelines did not specifically agree on what constituted a red flag, the majority did recommend a screen.

This screen consisted of a consideration for spe- cific historical characteristics, laboratory findings, and outcomes from physical testing that included sensibility testing, regional muscle strength testing, and reflex testing.14
A thorough consideration of: (1) patient history, (2) report of present compliant characteristics, and (3) physical examination and laboratory findings improves the likelihood of ruling in or ruling out the presence of red flags.

Historical characteristics include physical sys- tem changes, poor response to conservative care, and conditional considerations.

Physical system changes include pathological changes in bowel and bladder, pat- terns of symptoms not compatible with mechanical pain, blood in sputum, bilateral or unilateral radiculop- athy, numbness or paresthesia in the perianal region, writhing pain, nonhealing sores or wounds, unex-
Somatic Referred Pain (YES) Treat
Radiculopathy (YES) Treat with Caution plained significant lower or upper limb weakness, and progressive neurological deficits.

Along with consideration of a patient's present com- plaints, the clinician must consider how the patient's complaints change through the course of the day and/ or with previous treatment attempts.

The presence of serious pathology is suggested by: (1) pain that is worse during rest vs. activity, (2) pain that is worsened at night or not relieved by any position, (3) a poor response to conservative care including a lack of pain relief with prescribed bed rest, or (4) poor success with comparable treatments.

Finally, the presence of conditional charac- teristics such as litigation for the current impairment, long-term worker's compensation, and poor relation- ship with the employment supervisor could complicate a clinician's ability to interpret the complexities of a patient's vague or confounding clinical presentation.15
Using the examination to understand the source of a patient's referred pain is essential for appropriate diag- nosis, treatment, or referral to another specialist.16 When identifying red flags, numerous physical exami- nation and laboratory findings deserve consideration. Remarkable findings include, but are not limited to, pulsatile abdominal masses, fever, neurological deficits not explained by monoradiculopathy, clonus, gait defects, abnormal reflexes, and an elevated sedimenta- tion rate.

Because the seriousness of selected red flags warrants immediate action and others only require con- servative observation, it is important to categorize each finding and respond based on the level of seriousness the finding poses.
More subtle clinical findings can merit further con- siderations. One must consider how movement affects the patient's symptoms.

For example, one can consider symptoms that emerge distant from a site of insult and whether those symptoms can be modified by a patient's movement. Symptoms from radiculopathy are com- monly caused by a disc herniation and result in nerve inflammation and/or impingement.17

Other factors, such as degenerative changes, stenosis, and soft tissue growths, may trigger radicular symptoms.18 In any case, radicular symptoms can frequently be modified by a patient's movement.

However, while somatic and/or visceral referred pain emerges distant from the site of insult, the symptoms are not easily provoked with movements in the clinical examination.

Moreover, while somatic referred pain can respond to conservative care and/or interventional management, visceral referred pain requires attention from medical and/or surgical specialists, as it arises from organs such as the prostate, stomach, kidneys, or bladder.19

Few patient history identifiers are suggestive of spe- cific form of referred pain, but those that identify poten- tial red flags should not be overlooked. Additionally, the location of referred pain provides little assistance to diagnosis, as many referral distribution patterns over- lap.

However, the presence of referred pain during the examination should be systematically interpreted, as the response of pain reference may give insight into the patient's red flags. For example, report of referred pain during walking and a reduction of referred pain imme- diately upon sitting are suggestive of a stenosis-based disorder and a condition associated with myelopathy or radiculopathy.20

The symptoms associated with myelopathy are con- sidered more serious, because they generally involve spinal cord compression or injury. In myelopathy, char- acteristically the lower extremities are affected first, pro- ducing spasticity and paresis. The patient often exhibits a gait disturbance due to abnormalities that reflect dis- turbances in the corticospinal and spinocerebellar tracts within the spinal cord.

However, because myelopathy is a clinical diagnosis of upper motor neuron involvement, diagnostic decisions are made with a certain degree of uncertainty.21 Consequently, it is important to use tests that display high sensitivity to "rule out" the potential presence of this disorder.

For example, reflex tests designed to identify myelopathy such as the hyper- reflexive abdominal reflexes, lower limb deep tendon reflexes, and Babinski sign can be indicative of upper neuron dysfunction but must be considered in context with the entire clinical picture.

The use of sensibility (or sensation) testing, regional muscle strength testing, and deep tendon reflex testing may assist the clinician in identifying red flags and in differentiating radicular, somatic referred, and myelo- pathic symptoms.

Sensibility testing has been described in many ways and consists of a wide variety of applica- tion methods that include light touch, pain, vibration, and temperature testing. In most cases, sensation test- ing involves comparative analysis between extremities using any of the aforementioned modalities.

When carefully evaluated, abnormalities found during sensory testing can implicate a dysfunction of peripheral nerve fibers.22-24
Sensory changes can be found in the presence of myelopathy, which may confound the clinical picture when trying to rule out red flags. Generally, radiculo pathic changes are associated with dermatomal pattern losses, while myelopathic changes tend to exhibit mul- tiple dermatomal levels. Nonetheless, multilevel radicu- lopathic sensibility changes can demonstrate similar findings to myelopathic sensibility changes.

Thus, stand-alone sensation testing may or may not yield useful information, but is certainly an important screening characteristic when used in concert with other tests. However, because sensory testing lacks sensitivity, the absence of a sensation change does not rule out the presence of a red flag and should be valued only in concert with other tests and measures.

Regional muscle strength testing is designed to iden- tify if abnormalities in muscle strength are present dur- ing a one-repetition manual muscle test. However, in a similar fashion to sensibility testing, regional muscle strength testing may yield inconclusive findings second- ary to low levels of sensitivity. Additionally, any vari- ability in test outcomes may be related to differences in methods for measuring muscle strength.

For example, the method of manual testing for quadriceps strength varies among investigators and clinicians,25 where methods have ranged from asking the patient to straighten the leg and then the clinician offers resistance26,27 vs. asking the individual to push against the clinician's resistance while the knee remains flexed.28,29

Moreover, there may be differences in how the clinician uses the patient's body weight in the con- text of the test. Rainville et al. reported that out of four different methods of quadriceps testing (resisted knee extension, step-up test, knee-flexed test, and the sit-to- stand tests), the most reliable method for patients with L2-L3 impairment is a functional sit-to-stand test.25

The sit-to-stand test requires the patient to rise upon a single extremity using his/her own body weight as the resistance. Finally, the professional background of the tester may influence the value of test outcomes. For example, McCombe et al. reported that reliability between therapists for knee flexion and knee extension testing is good, but reliability among physicians and physical therapists is poor.30

Muscle stretch reflex testing (termed "deep tendon reflex" testing) is assessed by tapping over a selected muscle tendon with an appropriate testing instrument. The clinical utility of the test is based on the quality and magnitude of the response for normalcy.

Likened to sensation and regional muscle strength testing, deep ten- don reflex testing is often hampered by poor sensitivity. Deep tendon reflex testing is often subthreshold, result- ing in poor sensitivity and many false negative find-ings.31

For example, 25% to 30% of patients with abnormal reflexes demonstrate abnormalities in afferent and efferent pathways that are registered through elec- tromyography outcomes that are below threshold on a clinical deep tendon reflex test.32
To improve the understanding and investigation of red flags, we recommend a categorization approach to find- ings. Moreover, categorizing red flags into three distinct categories (Table 1) can aid the clinician in making the appropriate management decisions.33 The presence of selected red flags, such as pulsatile abdominal masses, unexplained neurological deficits, and recent bowel and bladder changes (Category I findings), suggests serious pathology outside the domain of musculoskeletal disor- ders and may require immediate intervention by an appropriate specialist.

A pulsatile abdominal mass may represent an abdominal aortic aneurysm and recent bowel and bladder changes are strongly suggestive of cauda equina and/or spinal cord compression. Unexplained neurological deficits may represent a neurologically degenerative disorder such as Gullian Barré, a central nervous disorder such as stroke or head injury, or a poorly differentiated form of radiculopathy.34

Other red flags such as a cancer history, long-term corticosteroid use, metabolic bone disorder history, age greater than 50, unexplained weight loss, and failure of conservative management (Category II findings) require further patient questioning and the clinician to adopt selected examination methods. Additionally, Category II findings are best evaluated in clusters with other examination findings.

For example, when evaluated individually, an age greater than 50 and long-term cor- ticosteroid use do not warrant immediate attention by a specialist. However, when both factors are present the likelihood of a spinal compression fracture is dra- matically increased and may merit increased attention from a specialist.20

Furthermore, isolated findings of failure of conservative management, unexplained weight loss, cancer history, or age greater than 50 rep- resent only minor concerns during a clinical screening.

Conversely, a concurrence of all four findings demon- strates a sensitivity of nearly 100% for identifying a malignancy.20
Selected red flag findings, such as referred or radiating pain (examples of Category III findings), are common, require further physical differentiation tests, and are likely to alter management. These symptoms have been described as "pain perceived as arising or occurring in a region of the body innervated by nerves or branches of nerves other than those that innervate the actual source of pain."35,36

This form of pain may arise from a number of pain generators including: (1) mechanically irritated dorsal root ganglia that are healthy, inflamed, or ischemically damaged, (2) mechanically stimulated nerve roots that have been damaged, (3) somatic struc- tures such as muscle, intervertebral disc, zygapophyseal joint, or sacroiliac joint, and (4) visceral structures such as the kidneys and/or prostate.37-41

Clinically, the way in which clinicians respond to each of the three categories of red flags depends on the clinician's intent for management. Many of the histori- cal and situational prevalence components are absolute or relative contraindications for selected treatment strat- egies.

Information obtained from present complaints may range from solicitation of appropriate medical consultation to the use of a multidisciplinary treatment plan. Any of the historical, physical examination or laboratory findings may function as a trigger to perform either neurological testing or upper and lower quarter screening, or both.

Upper and lower quarter screening consists of motor and sensory testing to evaluate the function of respective root levels serving the brachial and lumbosacral plexuses associated with the upper and lower extremities, respectively.
Patients with suspected head or cervical spine injury (including cases of unconsciousness or altered mental status) should be screened for neurological deficits and cervical spine fracture, dislocation, and laxity.43

Approximately 5% to 10% of unconscious patients who present to the Emergency Department as the result of a motor vehicle accident or fall possess a major injury to the cervical spine with a high probability of fracture and/or dislocation.44,45 Fifty percent of cervical spine fractures occur at either the C2 level or at the level of C6 or C7.46

Most fatal cervical instability injuries occur in upper cervical levels, either at craniocervical junction or at C1-C2.47,48 Two clinical decision-making criteria, the Canadian C-Spine Rules (CCR) and the National Emergency X- Radiography Utilization Group (NEXUS) criteria, allow clinicians to "clear" low-risk patients of cervical spine injury, obviating the need for radiography.49

To be clin- ically cleared using the CCR, a patient must be alert, not intoxicated, and not have a distracting injury (eg, long bone fracture or large laceration). The patient can be clinically cleared providing the presence of all of the following: (1) the patient is not high risk (age > 65 years); there is no history of paresthesias in the extremities or a dangerous injury mechanism, such as fall or impact, (2) the patient presents with low-risk factors that allow range of motion to be safely assessed, such as a simple rear-end motor vehicle collision, seated position in the Emergency Department, ambulation at any time post trauma, delayed onset of neck pain, and the absence of midline cervical spine tenderness, and (3) the patient is able to actively rotate the neck 45 degrees each to the left and right.

The NEXUS criteria state that a patient with sus- pected C-spine injury can be cleared providing that the patient presents with: (1) no posterior midline cervical spine tenderness, (2) no evidence of intoxication, (3) a normal level of alertness, (4) no focal neurological def- icit, and (5) no painful distracting injury.

Both the CCR study and NEXUS study have been prospectively vali- dated as being sufficiently sensitive to rule out clinically significant cervical spine pathology. The CCR were shown to be more sensitive than the NEXUS criteria (99.4% sensitive vs. 90.7%), where the rates of positive radiography were lower with the CCR (55.9% vs. 66.6%).

While debate still exists as to which criteria are more useful and easier to apply, both provide guidelines that can assist clinicians in effective screening decisions.49
he two mechanical conditions of the cervical spine that have unique pathological features (when compared to the thoracic and lumbar spine) and merit special atten- tion are upper cervical instability and vertebrobasilar insufficiency (VBI).

Congenital and hereditary condi- tions such as a variety of bone dysplasias that include Maroteux-Lamy syndrome, Morquio syndrome, and spondylo-epiphyseal dysplasia congenita have been asso- ciated with C1-C2 subluxation.

While laxity of the transverse ligament of atlas is a well-known consequence of trauma, infection, and rheumatoid arthritis, some patients present with atlantoaxial dislocation without a known predisposing cause.50,51 Surveys indicate 10% to 25% of patients with trisomy-21 have atlantoaxial lax- ity. Two-thirds of these cases are due to a laxity of the transverse ligament of atlas, whereas one-third of the cases are due to abnormal odontoid development.52

Although this association has been depicted on radio- graphs, the clinical incidence of serious cervical spine injury is not increased in this population compared to other populations.53 Approximately 25% of patients with rheumatoid arthritis have atlantoaxial instability, which is thought to be due to chronic inflammation and subsequent tissue deterioration.52

Congenital skeletal dysplasias may cause resultant odontoid hypoplasia, while Marfan syndrome may involve cervical ligamen- tous laxity and acute inflammatory processes can affect the retropharyngeal, neck, or pharyngeal spaces.54
Recognition of atlantoaxial laxity is of importance prior to management of cervical spine conditions. In obtaining the history, a review of any past fall, neck trauma, or head injury is essential.

Previous spine trauma may have resulted in an improperly healed odontoid injury that causes instability and neurological symptoms years later.55 Although traumatic lesions involving the atlantoaxial region are relatively rare, certain disease states and conditions present a higher theoretical risk of instability because of increased atlantoaxial joint laxity.

A complete review of the patient's medical history is valuable because many medical conditions are associated with an increased incidence of atlantoaxial laxity. Individuals with symptomatic atlantoaxial laxity may present with nonspecific symptoms that include neck pain, limited range of motion, torticollis, nausea, and dizziness. Additionally, a history of worsening symptoms (headache, fatigue, and transient upper extremity par- esthesias) with neck flexion is particularly revealing.56

Suspicion for ligament laxity in the upper cervical spine is heightened when the clinician observes positive laxity testing for the transverse ligament of the atlas (TLA) and alar ligament (Appendix A). The TLA laxity test and Sharp Purser test have been used to test the TLA and identify atlantoaxial subluxation.

The Sharp Purser test has demonstrated a predictive value of 85%, a specificity of 96%, and a sensitivity of 88% when atlan- toaxial subluxation was greater than 4 mm.57 The clini- cian must interpret the outcomes of these tests with caution, as the majority of these tests remain unevalu- ated for sensitivity or specificity.

Radiographic examination for upper cervical insta- bility has been reported in the literature.58-60 Upper cer-vical instability must be confirmed through dynamic imaging studies including open-mouth odontoid and lateral cervical spine radiograph.

On the open-mouth odontoid view, the combined spread of the lateral masses of C1 on C2 should not exceed 6.9 mm. A measured distance greater than 6.9 mm indicates rup- ture of the transverse ligament of atlas.55 Additionally, instability can be identified on flexion-extension views. An atlantoaxial distance greater than 4 to 5 mm, as demonstrated by lateral radiographs, is indicative of atlantoaxial laxity.55

An atlanto-dens interval of greater than 5 mm is indicative of laxity of the alar ligaments.55 Finally, the presence of retropharyngeal soft tissue swell- ing is an important finding for cervical spine trauma.55

Vertebrobasilar circulation should be screened, as occlusion may lead to transient ischemic attacks and cerebrovascular accidents.61

However, it is difficult to differentially diagnose the source of patient complaints, as the signs and symptoms overlap those of other more common benign entities (eg, labyrinthitis, vestibular neuronitis, benign paroxysmal positional vertigo). Ver- tigo is the hallmark symptom of patients experiencing ischemia in the vertebrobasilar distribution. Many patients describe their vertigo as nonviolent or more of a swimming or swaying sensation.

Other potential symptoms associated with VBI are: (1) visual distur- bances (diplopia), (2) auditory phenomena (sudden sensorineural hearing loss), (3) facial numbness or par- esthesias, (4) dysphagia, (5) dysarthria, and (6) syncope (drop attacks). In the clinical examination, sustained passive rotation of the cervical to the end range of motion can produce the symptoms.62

This test can dif- ferentiate VBI from benign paroxysmal positional vertigo (BPPV). For VBI, the test will produce the symp- toms that increase over time when rotation is sustained. Conversely, the same test will produce symptoms that will decrease over time in the presence of BPPV. More- over, the symptoms can be delayed by hours or even days in the presence of VBI.61
The cervical spine should additionally be screened for radiculopathies and myelopathies.

The onset of radicu- lopathies can be traumatic or insidious. Intermittent neck and shoulder pain (cervicalgia) is often present.63 Radic- ulopathy can be screened through the location of symptoms (nerve root sensory or motor distribution), inspection for atrophy, sensory, motor, and deep tendon reflex testing as well as the presence of a positive Spurling test (Appendix A). While the Spurling test maneuver has a sensitivity of 30% for cervical radiculopathy, it has a specificity of 93%.64

This suggests that the absence of a positive finding using the Spurling test does not provide compelling evidence of the absence of radiculopathy. Sensory, motor, and deep tendon reflex testing also suf- fers from poor sensitivity and can result in missing the presence of radiculopathy that is actually present.33

Cervical spine myelopathies are the most common cause of nontraumatic paraparesis and tetraparesis. The process usually develops insidiously; patients often present with only a stiff neck in early stages. Addition- ally, they may present with stabbing pain in the preaxial or postaxial border of the arms. Patients with a high compressive myelopathy (C3-C5) can present with a syndrome of numb, clumsy hands accompanied by a loss of manual dexterity, difficulty with writing, nonspe- cific diffuse weakness, and abnormal sensations.65

Patients with a lower cervical myelopathy typically present with a syndrome of weakness, stiffness, and proprioceptive loss in the legs accompanied by signs of spasticity and gait disturbances.
Weakness or clumsiness of the hands may be observed in conjunction with weakness in the legs, whereas motor loss in the hands with relative sparing of the legs is relatively rare.

Loss of sphincter control and urinary incontinence are rare, but selected patients complain of urgency, frequency, and urinary hesitancy.66 The most typical examination findings are suggestive of upper motor dysfunction, including hyperactive deep tendon reflexes, ankle and/or patellar clonus, spasticity (especially of the lower extremities), and Babinski sign.

The scapulohumeral reflex allows evaluation of dys- function in the upper cervical spine (C1-C4),6 while the Lhermitte's sign (midline thoracic spine tingling pro- duced with cervical flexion) is useful to diagnose spinal cord conditions including multiple sclerosis, tumors, and other spinal cord compressive pathologies (Appendix A).67 If unilateral symptoms that include hemiparesis/hemiparalysis and sensory changes are present on one side of the body, Brown-Séquard syn- drome should be considered. Brown-Séquard syndrome can be caused by any of the multiple mechanisms reported in the literature that result in damage to one side of the spinal cord.68

The most common cause remains traumatic injury, often a penetrating mecha- nism such as a stab wound, gunshot wound,69 or a unilateral facet fracture and dislocation due to a motor vehicle accident or fall. Numerous nontraumatic causes have been reported, including tumor (primary or meta- static), multiple sclerosis, disk herniation, herniation of the spinal cord through a dural defect, epidural hematoma, vertebral artery dissection, transverse myeli- tis, radiation, intravenous drug use, and tuberculosis.70
Numerous Category I red flags can be witnessed in concert with a thoracic pain presentation. As a conse- quence of viscerosomatic referred pain, numerous vis- ceral conditions can produce secondary musculoskeletal pain in the thoracic region.

This pain production is a consequence of the complex visceral afferent nerve sup- ply that begins in the afflicted organ and terminates in the sensory region of the spinal cord, converging with somatic afferents from respective musculoskeletal struc- tures of the thoracic spine.

Increased afferent activity from the visceral structures creates increased ascending pain information projecting to areas of the midbrain that also receive information from musculoskeletal structures. As a result, the patient experiences pain in selected regions of the musculoskeletal system in response to the convergent visceral afferent signals from the involved organ.72,73

Viscerosomatic pain referral produces midline pain that is accompanied by neurovegetative signs and pos- sible emotional reactions. The referred pain and hyper- algesia felt in the trunk is associated with sensitization of dorsal horn neurons.74,75 Thus, patients could expe- rience symptoms in the musculoskeletal structures in- nervated by the same nerve levels at which the visceral afferents converge.

An example of this response is acute myocardial inf- arction. Increased visceral afference from the heart results in referred pain that can be felt in the left pectoral and upper extremity regions, or the lower sternal and epigastric region, as well as the associated pallor, sweat- ing, and nausea that often characterize this serious con- dition.

The musculoskeletal pain could be interpreted as a musculoskeletal disorder, if not for the history and accompanying symptoms. Visceral conditions, however, are not the only situations that create this form of eferred pain. Additionally, inflammation, neoplasm, and metabolic disorders can produce similar referred symptoms.76 Moreover, myofascial pain syndromes have been attributed to similar neurophysiological adapta- tions.

These syndromes result in similar pain reference patterns in the musculoskeletal system, including the thoracic spine region.77-80
Primary tumors, metastatic disease, metabolic dis- eases, and fractures can produce viscerosomatic reflexes and pain.81,82 The thoracic spine demonstrates the high- est incidence in the entire spine for primary neoplasm and metastatic tumors.

The thoracic region appears to be a principle location for primary tumors that include osteoblastoma, chondrosarcoma, and multiple myeloma.83,84 Moreover, it appears to be a common target for metastatic disease originating from prostate cancer in the males and breast cancer in the females, as well as bronchial carcinoma and/or pancoast tumor from both groups.85

These conditions typically produce severe central thoracic pain, marked thoracic movement limitations, and potential intercostal neuralgia if the tumor reaches the segmental nerve.
The incidence of thoracic intervertebral disc lesions is greater than once thought, commonly resulting from trauma, degeneration, lifting, or even exercise.94,95 This requires careful differential assessment as a disc lesion can mimic symptoms of visceral conditions, includ- ing afflictions of the cardiac, pulmonary, or renal systems.96-98

While intercostal neuralgia is a possible sequelae of a primary thoracic disc herniation,94,99 disc lesions can exist without the peripheral symptoms when the segmental nerve exits in a far cranial position relative to the location of the intervertebral disc. Moreover, not all anterior and lateral trunk pain is radicular in nature.

Disc-related symptoms in the thoracic spine appear to be related to the severity of the tissue failure and the resultant structures that are impacted. Mild disc lesions may simply produce referred pain as previously dis- cussed. Severe extrusion can result in a gambit of symptoms including nonradicular and radicular pain associated with sensitization of nociceptive afferents in surrounding tissue and the segmental nerves.94

These symptoms can be accompanied by sensory changes that include paresthesia, dysesthesia, and/or complete sen- sory loss associated with compromise to the blood sup- ply and axons in the afferents of the segmental nerve.

Finally, this condition can present with myelopathic symptoms from spinal cord deformation, including cold feet, electric shocks and hyper-reflexia in the lower extremities, coordination loss, ataxic gait, and/or bowel/ bladder disturbances.94,99

Disc calcification is a noteworthy complication of central thoracic disc herniation, potentially leading to spinal cord compression.100 The disc, however, is not the only structure whose calcification can compromise the diameter of the spinal canal.

Ossification of the poste- rior longitudinal ligament has also been documented,101 as has flaval ligament ossification.102,103 Any of these changes can produce a compromise to the spinal canal diameter, potentially lending to the previously discussed symptoms associated with myelopathy.
Numerous conditions could be categorized as Category II red flags in the lumbosacral spinal region. For exam- ple, in a similar fashion to the thoracic spine, the lumbar vertebrae are at risk for compression fractures in the context of osteoporosis.107 Risk factors similar to those in the thoracic spine can be observed in this region.
Numerous pyogenic infectious conditions can emerge in the lumbosacral region, producing fever, malaise, poten- tial bowel and bladder disturbances and severe low back

Vertebral osteomyelitis can produce these symptoms, where Poyanli et al. observed a pneuomococcal osteomyelitis in response to recent meningitis in a patient with immunosuppression.108 Others have reported pyogenic spondylodiscitis related to direct inoculation, contiguous spread, and hematogenous seeding.109

Specifically, spondylodiscitis can occur in the lumbar spine in response to previous discography110,111 or nucleoplasty,112 as well as general procedures such as colonoscopy, organ tissue biopsy, and oocyte retrieval for in vitro fertilization.113,114

In addition, this condition can emerge in response to invasive procedures leading to bacteremia. For example, Yavasoglu et al. reported the incidence of spondylodiscitis in association with blood-borne streptococcal endocarditis.115

Other inves tigators have reported brucellosis spondylodiscitis that was associated with adjacent vertebral body infection and abscesses in the adjacent paravertebral muscles.116,117
The disc does not appear to be the only structure capable of producing these clinical findings in response to infectious processes.

Narvaez et al. found increased incidence of spontaneous pyogenic zygapophyseal joint infection in injection drug abusers and in those patients with a history of prior spinal instrumentation.118
Okada et al. diagnosed lumbar zygapophyseal joint infection associated with epidural and paraspinal abscess that produced fever and severe low back pain that radiated into both buttock and thigh regions.119 However, this condition does not have to present with a predisposing clinical condition, as it can develop idiopathically.120

Conversely, numerous arthritides involving the zygapo- physeal joints can present with nontraumatic onset and possible fever, including rheumatoid arthritis, systemic lupus erythematous, ankylosing spondylitis, and gout.121-125

Not only can these conditions affect the zygapophy- seal joints, but the sacroiliac joint can be affected by them as well. Numerous nontraumatic etiologies can lead to unilateral and/or bilateral sacroiliac symptoms.71 Nontraumatic low back pain can emerge from numer- ous arthritides of the sacroiliac joint, including tubercu- lous infection,126,127 ankylosing spondylitis,124,125 brucellosis,128,129 and Reiter's syndrome.130

Moreover, investigators have reported that patients with Crohn's disease and inflammatory bowel disorder can present with sacroiliitis of nontraumatic onset.131
Because numerous organic and nonmusculoskeletal con- ditions can produce pain in the lumbopelvic region, appropriate physical examination assists in the differen- tial diagnosis.

Specific testing for sensibility, strength, reflexive and neurodynamic function have been used in the evaluation of the lumbosacral spine. However, their utility is questionable and must be evaluated in context with the patient's symptom presentation.

Aronson and Dunsmore indicated that sensory deficits to pin prick involving L3 and L4 root levels were noted in 39% of patients with L2-L3 disc herniation, and in 30% of patients with problems at L3-L4, verified intraopera- tively.132

Others have found 60% of patients had sen- sory impairments from L3-L4 lesions and 52% at L4- L5 lesions.25 Jonsson and Stromquist reported that der- matome sensory disturbance was present in 60% of patients with sciatica.133 Blower found 62% of patients with sensory disturbances134 and Jensen reported that just 56% of patients with sciatica of a L4 distribution demonstrated neighboring sensory disturbance and L5 distributions.135

Finally, Lauder et al. found a sensitivity of 55% in a population of patients with lumbar radic- ulopathy and abnormal electrodiagnostic test values, whereas specificity scores were slightly higher (77%).136

Hakelius and Hindmarsh reported that quadriceps weakness was present in only 1% of the population operated for lumbar disc herniation, including any lum- bar level in the analysis.137 Aronson and Dunsmore ound much higher values, where weakness was discov- ered in 30% of individuals with L2-L3 disc herniation and 37% of individuals with L3-L4 disc herniation.132

Rainville et al. found quadriceps weakness in 70% of patients at L3-L4 and 56% of patients at L4-L5.25 The authors found ankle dorsiflexion weakness in 30% of subjects with an L4-L5 herniation and just 9% with extensor hallucis longus weakness associated with the same lesion. Lauder et al. evaluated any form of lower extremity weakness and recorded a sensitivity of 69% and specificity of 61% for using the test to identify lumbar disc herniation.136

Spangfort reported that unilateral impaired patella reflexes were evident in 35% of patients who required surgery for L2-L3, 48% for L3-L4, 6% for L4-L5 and L5-S1 combined disc herniations.138 Patellar reflex abnormalities were noted by others in 60% of patients with impaired L3 root function vs. 65% in patients with impaired L4 function.25

In Rainville et al.'s study, many of the subjects with normal clinical reflex tests concur- rently demonstrated impaired quadriceps strength. Lauder et al. examined individuals with lumbar radicu- lopathy, verified through electrodiagnostic testing.136 They reported that the clinical utility of the patellar reflex resulted in higher diagnostic values than the Achilles reflex test.

The straight leg raise (SLR) and the slump sit test (SS) are purported tests and measures for lower lumbar radiculopathy and in past studies have demonstrated similar diagnostic values (Appendix A). The SLR and SS both exhibit moderate sensitivity and poor specificity as diagnostic tests.71,139-142

The poor specificity is associ- ated with the membranous connections from the root dural sleeve to the posterior longitudinal ligament and posterior disc,143-146 which may account for nonradicu- lar, referred low back symptom provocation in the pres- ence of dural tensioning.147 Similar test procedures have produced nerve root and dural movement in previous investigations.148,149

Thus, considering the nociceptive innervation of the dura and posterior longitudinal ligament,145,150,151 any subsequent tension load that is imposed on the root could produce nonradicular referred pain by virtue of chemosensitivity and mecha- nosensitivity of the root, root sleeve, posterior longitu- dinal ligament, and/or posterior outer annulus of the lumbar intervertebral disc.152-154

This suggests that the SLR and SS test outcomes should be interpreted in con- text with the patient's presenting symptoms. In the event of radiculopathic presentation, these tests serve as screening tests for the presence of radiculopathy.155

Con-versely, the tests can also be positive in nonradicular low back pain, suggesting involvement of the anterior thecal sac in response to mechanical duress of the dural struc- tures.156 Finally, a negative finding of the SLR or SS could provide greater clinical value than a positive find- ing, suggesting that clinicians should routinely include such tests in the clinical examination.
Low back pain (LBP) is a significant problem that affects approximately 50% of the population.1 The majority of individuals with recurrent episodes of LBP do not have an identifiable structural diagnosis.2 A treatment-based classi- fication system has been developed to identify similarities among subsets of individuals with LBP so that clinicians can select appropriate interventions to improve out- comes.3, 4 One subset of the classification system includes individuals who are thought to benefit from spine stabi- lization exercises.5-7

The stabilization classification is a subgroup of patients who experience LBP as a result of faulty neuromuscular control, rather than from true ligamentous instability.8, 9 Muscular injury, fatigue, or facet or disc degeneration can compromise the stabilizing effects resulting in shearing forces that cause the pain.10

A decrease in muscular con- trol can have damaging effects on postural control and intersegmental stability which may lead to degeneration of spinal structures.10 Therefore, this subgroup of patients would likely respond to a spinal neuromuscular rehabili- tation program that targets the spinal stabilizers.

The abdominal drawing-in maneuver (ADIM) has been described as the best way to activate the TrA11-14 and is often a fundamental exercise in a traditional stabilization program for LBP.15, 16 The ADIM is an inward movement of the lower abdominal wall in which the patient is instructed to draw the umbilicus
toward the spine.15, 16

A key feature is to teach the patient to preferentially activate the TrA while maintaining relaxation of the more superficial musculature (rectus abdominus, external oblique). The ADIM is often used to facilitate the re-education of neuromuscular control mechanisms provided by the local stabilizing mus- cles.16

This training of the TrA has been shown to improve pain and function in patients with chronic LBP17-19 because activating these mus- cles is thought to assist in dynamic spine stabilization during functional tasks.20

ostures including supine or prone and advancing from stable to increasingly unstable surfaces.16, 17 The tradition- al stabilization exercise interventions have been successful at treating LBP,17, 21-24 however there is often recurrence of LBP that has been illustrated in several stud- ies.20,25-30 This recurrence rate may be an indicator that patients may be performing these exercises without prop- erly activating the TrA or that a timing dysfunction exists.

Hodges et al.25 proposed that the TrA contracts prior to limb movement in healthy individuals, while the pre-acti- vation is poor in those with LBP. Exercise intervention should focus on the best method to target the stabilizing musculature, and therefore the recruitment of the TrA during specific exercises should be examined.

Sling exercise therapy has been proposed to activate local spine stabilizers during the activity in a pain free manner without substitution of global muscles.26 Sling therapy exercise is performed while the pelvis or lower extremities are supported or suspended in a sling (Figure 1).

The exer- cises can be made easier by providing assistance with a sling and elastic cord to offset body weight, or made more difficult by providing an unstable surface to perform the exercises. Thepatientmustbearweightthroughthecords and balance him or herself during the exercise.

Stuge et al. found that doing specific stabilization exercises using sling exercise therapy in post-partum women with pelvic pain was effective in reducing pain, improving functional status, and improving health-relating quality of life after a 20 week inter- vention27 and at a 2 year follow up.28 However, the underlying mechanism for improvement in their outcomes was unknown.

Stuge proposed that increased activation of local stabilizer muscles with the sling exercise thera- py may have contributed to improved outcomes compared to traditional therapy.

Rehabilitative Ultrasound Imaging (RUSI) is a non-invasive method to visualize the lateral abdominal wall and qualitatively and quantitatively assess deep muscular activity with exercise.

Muscle thickness change during the ADIM has been validated with EMG studies29,30 and is an indica- tor of muscle activation.16, 31 The TrA activation ratio
has been devel- oped to examine the recruitment of the TrA during an active con- traction, thus normalizing the measurement to the resting thick- ness of the muscle.32

Therefore, comparisons in the TrA activa-tion ratio during specific therapeutic exercise interventions can help identify those exercises that preferentially recruit the local stabilizers.16 The purpose of this study was to compare the TrA activation ratio during a progression of traditional sta- bilization exercise to a similar progression of sling based exercise.
The RedcordTM sling exercise therapy device (Redcord AS; Staubo, Norway) was used for the sling bridge exercise. There were four possible levels of the sling-bridging exercise (Figure 6). The partici- pants in the sling exercise group began by laying supine on the treatment table with their hips and knees bent to 90o. The partic- ipant's knees were placed in a sling that was suspended from the ceiling. Thefirstlevelconsistedoftheparticipantsliftingtheirhips into the air while maintaining straight alignment of the knees, hips, and shoulders.

Participants were not instructed to perform an ADIM prior to sling exercise, as suggested in product literature (RedCordTM). The participants held this position for 5 seconds while an image was recorded then lowered themselves back to the start- ing position. In the second level, the participants left knee remained in the sling and the right knee was not in the sling.

The participant was instructed to hold their right leg at the same level as the left and to lift their hips into the air while maintaining straightalignmentoftheknees,hips,andshoulders. Theyheldthis position for 5 seconds and then lowered back to the starting posi- tionInthethirdlevel,theparticipanthadbothkneesplacedinthe sling and a DynaDiscTM was placed in between their scapulae to pro- vide an unstable proximal surface upon which to perform the bridge.

In the fourth level, the participants' ankles were placed in two separate slings and they were instructed to perform the bridge and then abduct their legs one at a time before lowering back to the starting position. Participants performed 5 repetitions on each level of the exercise and US images were recorded on repetitions 2-4.

The traditional exercise and sling exercise groups did not differ (P >.05)intermsofdemographic stabilizationclassificationcriteria, or pre-intervention TrA activation ratio. It was not possible to obtain clear images for 2 participants; therefore the data for these participantswasnotincludedintheanalysis. Allparticipantswere able to progress through the first two levels of their respective exer ciseprogressioninapainfreemannerwithcorrecttechnique. One individual was not able to progress to Level 3 of the traditional bridging exercise, while all individuals in the sling bridge progres- sion were able to complete Level 3.

Level 4 presented the greatest technical challenge with 18 (75%) individuals able to complete the traditional bridging exercise and 22 (88%) individuals completing the sling bridge progression. No individual in either group report- ed pain during the exercise intervention at any level.

Although consistently higher in the sling exercise group, there were no significant differences (P>.05) in TrA activation ratios between traditional bridging and sling bridging when comparing the first 3 levelsoftheexerciseprogression(Table2). TrAactivationratiowas significantly greater (P=.04) when performing sling bridging with hip abduction (Level 4) compared to traditional bridge with hip abduction (Table 2).
The goal of a rehabilitation program for patients with LBP is often based on an ability to regain neuromuscular control of the TrA, in conjunction with other segmental stabilizers such as the multifidus. This treatment is the recommended plan for "stabilization" classifi- cation of LBP patients who may have poor motor control especial- ly during dynamic tasks. These patients are typically young, have increased flexibility and experience recurrent episodes of LBP.

On examination, there is typically a positive prone instability test37 or other provocative maneuvers that amplify abnormal motion in the spine. These individuals often present with subacute symptoms and may function at a relatively high level despite ongoing or recurrent LBP.

The TrA activation ratio has been proposed as an index to deter- mine the ability of the local musculature to stabilize the spine.29,32,38

There is a preponderance of literature that has utilized ultrasound imaging to examine the function of the TrA reporting either mus- cle thickness during contraction39,40 or the difference in thickness during contraction compared to a resting state.41 The TrA activation ratio compares the muscle thickness during contraction to the thickness during a resting state in a similar manner to the method that reports strength measures as normalized to body weight.

Although the terminology of "activation" ratio implies a neuromus- cular influence, ultrasound imagining is only able to measure cross sectional thickness of the muscle rather than a true measure of the reactivity or excitability of the specific muscle being examined.

Changes in thickness are thought to be representative of increased muscle activation.29,42 Although the TrA activation ratio seems to be the most consistent and representative measure, normative data for the TrA activation ratio in both normals and individuals with LBP is lacking.43

Average TrA activation ratio during the ADIM for both groups prior to the intervention was 1.58. This ratio seems low compared to a previousstudybyTeyhenetal34 whoobservedTrAactivationratios of approximately 2.0 during the ADIM.

However that study used active duty soldiers with non-specific LBP and utilized ultrasound imaging for biofeedback during the testing.34 The TrA activation ratio observed in the present study was consistent with the values reported by Kiesel et al.44 for those with stabilization classification LBP where there was a 50% increase in thickness during contrac- tion.
Cervical spine injuries in the athlete account for 10% of the 10,000 cervical spine injuries that occur in the United States annually [1]. Cervical spine injuries can happen to the athlete at any level of participation ranging from unsuper- vised activities to organized contact and collision sports. These injuries may occur in such sports as diving, surfing, skiing, football, boxing, lacrosse, wrestling, soccer, rugby, ice hockey and gymnastics.

The incidence of complete quad- riplegia among high school and college football athletes has been reported to be as high as 2.5 per 100,000 in 1976 and as low as 0.5 per 100,000 in 1991 because of system-wide pro- tective equipment and rule changes [2].

The potential cata- strophic nature of cervical spine injury has invoked consider- able effort by both the medical and athletic communities to determine risk factors and return to play criteria.

The decision on whether to let an athlete return to play should be based on medical parameters, such as the athlete's medical history, physical examination, the presence of im- aging abnormalities, as well as psychosocial and demo- graphic factors such as age and level of competition. Sev- eral authors have recommended guidelines for return to play [3-9], but such standardized criteria have not been uni- formly accepted by the medical community.

Morganti et al. [10] surveyed 113 physicians in reference to their return-to- play recommendations for 10 case histories. The authors were unable to reach a consensus on the postinjury manage- ment because of each injury's unique and individual presen- tation.

In addition, in the majority of the cases there was no relationship between return-to-play recommendations and the medical consultant's years in practice, subspecialty training or the use of published guidelines.
Cervical spinal cord neurapraxia with transient quadri- paresis usually presents as temporary bilateral burning par- asthesia and is associated with various degrees of bilateral extremity weakness. Its incidence in collegiate football players is approximately 1.3 per 10,000 athletes [11]. The mechanism of injury is usually cervical hyperextension, al- though other pathomechanisms can result in cervical spinal cord injury. The neurologic abnormalities include varying degrees of motor and/or sensory disturbance affecting two to four limbs.

The duration of these symptoms and signs is usually relatively short, on the order of 10 to 15 minutes. However, some patients may have residual symptoms for up to 36 hours. Sensory disturbances vary from burning pain to loss of sensation. Motor abnormalities range from bilateral upper and lower extremity weakness to complete paralysis.

Transient quadriplegia is associated with developmental cervical stenosis, kyphosis, the presence of a congenital fu- sion, cervical instability and/or an intervertebral disc protru- sion or herniation. Vascular and metabolic etiologies may also play a role in transient quadriplegia [11].

Torg et al. [12] developed the Torg ratio (defined as the an- terior-posterior diameter of the spinal canal measured as the distance from the midpoint of the posterior aspect of the verte- bral body to the nearest point on the corresponding spinolami- nar line divided by the anteroposterior width of the vertebral body) to evaluate congenital stenosis of the cervical spine. They found that this radiographic sign was extremely sensitive (greater than 90%) but had an extremely low positive predic- tive value for determining future injury.

This low positive pre- dictive value precludes its use as a screening method for par- ticipation in contact sports. Further Herzog et al. [13] determined that the Torg ratio has a very low positive predic- tive value (approximately 13% in professional football play- ers) for the presence of true spinal stenosis, thereby limiting its value for even evaluating the athlete for cervical stenosis.

Maroon and Bailes [1] have developed a three-stage clas- sification system for the treatment of athletes with cervical spine injuries based on the neurologic symptoms involved. Type 1 injuries consist of patients with permanent spinal cord dysfunction. These include patients with a complete spinal cord injury or incomplete lesions, such as an anterior cord syndrome, Brown-Sequard syndrome, central cord syndrome or mixed incomplete syndrome. Type 2 injuries are transient spinal cord injuries, such as spinal concussion, neurapraxia or "burning hands syndrome."

Type 3 injuries consist of disorders involving radiologic abnormalities without neurologic deficit, that is, congenital and acquired spinal stenosis, herniated discs, unstable fractures and/or dislocations, stable spinal fractures (lamina, spinous process and minor portion of vertebral body), unstable ligamentous injuries and spear tackler's spine.
The "stinger," which is common in contact and collision sports, such as football and rugby, is described as a tempo- rary episode of upper extremity unilateral burning dysesthe- sia with motor weakness. Stingers may occur in as many as 50% of athletes involved in contact/collision sports [3,14].

Patients usually describe a painful sensation that radiates from their neck to their finger tips after an impact load to the neck or shoulder. The deltoid (C5), biceps (C5,6) and spinati muscles (C5,6) are most commonly involved. The complaints of pain usually last for a few seconds to minutes, but symptoms and signs (particularly weakness) may persist for as long as a few weeks [1,15,16].

Three different mechanisms have been proposed for a stinger: 1) stretch or traction injury to the brachial plexus, 2) extension of the cervical spine resulting in nerve root com- pression within the neural foramina and 3) a direct blow re- sulting in injury to brachial plexus.

This last mechanism in a football injury is thought to result from compression of the fixed brachial plexus between the player's shoulder pad and the superior medial scapula as the pad is pushed into the area of Erb's point (point of fixation of the upper trunk of the brachial plexus to the transverse process) [16].

Chronic recurrent stingers have been described as a recurrent neura- praxia or axonotmesis of the cervical nerve roots, often in the setting of cervical disc degeneration [15-17]. The C5 and C6 nerve root distributions are most commonly af- fected.

The reported annual incidence of a stinger is be- tween 49% and 65% in collegiate-level football players.
Meyer et al. [17] studied 266 collegiate football players and found that 40 of these players (15%) had reported a symptomatic stinger with 31 athletes (11.6%) complaining of associated neck pain. Of the 40 symptomatic patients, 34 (85%) reported an extension-compression mechanism, whereas 6 players (15%) noted a brachial plexus stretch eti- ology.

The mean Torg ratio was lower for the athletes with a history of a stinger (less than 0.8 in 47.5% of the players) as compared with the asymptomatic group (less than 0.8 in 25.1% of the players). Players with a Torg ratio of less than 0.8 had a three times greater risk of incurring a stinger than the players with ratios greater than 0.8.

The authors noted that 45% of the athletes with a previous history of a stinger would have recurrent episodes. It should be noted that the stingers these athletes sustained were probably a result of foraminal compromise, resulting in radiculopathy.

It should also be noted that the Torg ratio was not developed to assess for foraminal narrowing, and therefore studies like this by Meyer et al [17], although confirming the role of foraminal stenosis in the development of a stinger, tend to confuse the literature regarding the value of the Torg ratio.
A difficult management scenario for the team's physi- cian is deciding when an athlete may return to a competitive level of activity after his or her spinal injury. Several au- thors have published guidelines for return to play after cer- vical spinal cord injury.

Torg and Ramsey-Emrhein [6] outlined a series of guidelines for the return-to-collision activities in patients with developmental stenosis of the cervical spinal canal af- ter cervical cord neurapraxia. He categorized cervical con- genital, developmental and posttraumatic conditions as no contraindication, relative contraindication or absolute con- traindication to the return-to-collision activities.

Relative contraindication to play was defined as the possibility for recurrent injury despite the absence of any absolute con- traindication to participate in contact/collision sports. The patient had to understand that the degree of risk for re-in- jury was uncertain.

For example, an asymptomatic athlete with a Torg ratio of less than 0.8 without any other cervical abnormality may return to sports without contraindication. However, a Torg ratio of less than 0.8 and one previous ep- isode of a spinal cord neurapraxia with or without interver- tebral disc disease and/or degenerative changes represent a relative contraindication for return to play.

Absolute con- traindications to return to play include a previously docu- mented episode of neurapraxia with magnetic resonance imaging (MRI) findings of a cord abnormality, that is, edema, a documented episode of cervical cord neurapraxia associated with ligamentous instability, neurological symp- toms for greater than 36 hours and/or multiple episodes of neurapraxia [6].

Using a newly developed computer technique for measur- ing anatomic structures by means of MRI, Torg et al. [5] measured the spinal cord and canal diameters of 53 of 110 cases of documented cervical cord neurapraxia.

The author found an overall recurrence rate of 56% in players returning to contact/collision sports, although individuals with uncom- plicated cervical cord neurapraxia did not have a higher risk for permanent neurologic injury. The risk of recurrence was increased with small Torg ratios (strongly predictive), smaller absolute disc level canal diameters and less space available for the cord.

Unfortunately, only 48% of patients in this study were evaluated with MRI, making anatomic and imaging comparisons between those who returned to play and those who did not impossible. Additionally, in the population of players who returned to contact/collision sports, follow-up averaged only 3.3 years, making definitive conclusions as to the risk of future neurologic injury uncertain [18].

After reviewing the literature and clinical data, Torg and Ramsey-Emrhein [6] set out to determine reasonable guide- lines for the return to contact and collision sports for an ath- lete after a cervical spine injury. The following spinal con- ditions are considered by Torg to have no contraindications to participation in contact/collision sports:

1. Congenital conditions, such as a type 2 Klippel-Feil anomaly (which involves only a one- or two-level cer- vical fusion with full range of motion, no evidence of instability or the presence of cervical disc disease or other degenerative changes).
2. Spina bifida occulta.
3. Patients with healed stable nondisplaced fractures
without sagittal malalignment.
4. Patients with asymptomatic disc herniations treated
conservatively in the past.
5. Asymptomatic patients after a one-level anterior or
posterior cervical fusion for miscellaneous reasons who are neurologically intact, pain free and have a solid fusion.

Relative contraindications [6] to returning to contact/col- lision sports include a patient with full cervical motion, no pain and a normal neurologic examination with:

1. A previous upper cervical spine fracture, such as a healed nondisplaced Jefferson fracture, a healed type 1 or type 2 odontoid fracture and/or a healed lateral mass fracture of C2.
2. A healed stable, minimally displaced, vertebral body compression fracture without sagittal malalignment. 3. A healed stable fracture of the posterior elements,
excluding spinous process fractures.
4. The presence of minimal residual facet instability af-
ter surgical or conservative treatment of cervical disc
5. After a healed two- or three-level cervical fusion.

Absolute contraindications [6] to returning to contact/ collision sports include:

1. Odontoid anomalies.
2. An atlantooccipital fusion.
3. Atlantoaxial instability.
4. Atlantoaxial rotatory fixation.
5. Certain Klippel-Feil anomalies (type 1, defined as a mass fusion of the cervical and upper thoracic verte- brae, or a type 2 lesion with associated limited motion and/or associated occipitocervical anomalies or insta- bility with or without disc disease and other degenera- tive changes).

The radiographic presence of a spear tackler's spine, defined as a subset of football players who exhibit developmental stenosis of the cervical canal, persis- tent reversal of the normal lordotic cervical spine on neutral lateral X-ray films, posttraumatic findings on roentgenograms and/or documented history of using a spear tackling technique [19].

Subaxial spinal instability defined by lateral roent- genograms that show 3.5 mm or more of horizontal displacement of one vertebrae on the other or greater than 11 degrees of rotation difference as compared with the adjacent vertebrae as measured on a lateral or flexion-extension radiograph [20].

An acute fracture of either the body or posterior ele- ments with or without ligamentous instability. Healed subaxial vertebral body fractures with sagit- tal malalignment.

An acute fracture of the vertebral body with associated posterior arch fractures and/or ligamentous laxity. Residual bony canal compromise from retropulsed bony fragments.
Continued pain, abnormal neurological findings or limited motion from a healed cervical fracture.

The presence of a symptomatic acute soft or chronic disc herniation with associated neurological find- ings, pain or limited motion.

After a successful one-level fusion in the presence of diffuse congenital narrowing of the cervical canal.

Cantu et al. [3,4] presented guidelines for return-to-con- tact/collision sports after transient quadriplegia based on case studies.

They proposed that an athlete may return to contact/collision sports after the first episode of transient quadriplegia if there is complete resolution of symptoms, full range of motion and a normal cervical spinal curvature without evidence of spinal stenosis on MRI, computed to- mography (CT) or myelography. Relative contraindication to the return to sports included the presence of mild or mini- mal disc herniations and transient quadriplegia caused by minimal contact.

They though that "functional" spinal steno- sis (defined as a loss of the cerebrospinal fluid around the cord or as deformation of the spinal cord as documented by MRI, CT with contrast or myelography) was an absolute contraindication to return to sports.

Using their injury classification system described above, Maroon and Bailes [1] concluded that patients with type 1 injuries should not be allowed to return to sports.

Patients with type 2 transient injuries may be allowed to return to contact activities if a thorough workup is negative and neu- rologic symptoms do not recur. If the athlete experiences multiple episodes of these type 2 injuries, serious consider- ation for disallowing return to contact and collision sports should be given.

Type 3 injuries need to be evaluated on a case-by-case basis, because some injuries may not be stable under high-impact athletic activities. Athletes with a spear tackler's spine, unstable fracture and/or dislocation, as de-scribed by White et al. [20] and ligamentous instability re- quiring a orthosis or surgical treatment should be prevented from returning to contact/collision sports.

Other type 3 inju- ries, such as herniated intervertebral discs treated surgically, stable fractures of the cervical spine, congenital spinal stenosis and cases of congenital spinal fusion (except Klip- pel-Feil syndrome, a narrowed spinal canal, multilevel fu- sion or instability on flexion/extension views) may safely return to contact sports [1].
Weinstein [7] has recommended that the decision for re- turn to play after a stinger be based on both clinical and electrodiagnostic studies.

After a stinger, those individuals who have demonstrable weakness that persists beyond 2 weeks are scheduled to undergo electromyographic evalua- tion. Players who demonstrate clinical weakness and mod- erate fibrillation potentials are withdrawn from play.

Should sequential electromyographic studies reveal no spontaneous potentials or only mild or scattered positive waves, and if motor unit recruitment reveals changes consistent with rein- nervation, the athlete may return to his or her preinjury level of activity, providing there is also clinical improvement with full pain-free cervical motion and return of normal strength.
The issue of return to play for an athlete after a cervical spine injury is controversial. It should be emphasized that there are no firm criteria for return to play, although most au- thors agree on many specific issues.

Tremendous extrinsic pressures may be exerted on the physician from noninvolved and involved parties in regard to returning an athlete to com- petitive activities. The decision to return an athlete to a par- ticular sport should be based on the mechanism of injury, objective anatomical injury (as demonstrated by clinical ex- amination and radiographic evaluation) and an athlete's re- covery response.

Because of the potential for significant cata- strophic sequela from premature or inappropriate resumption of athletic participation, an understanding of the natural his- tory of specific clinical syndromes and inherent risk factors should be familiar to the treating physician.

The issue of return to play for an athlete after a cervical spine injury is controversial. It should be emphasized that there are no firm criteria for return to play, although most au- thors agree on many specific issues. Tremendous extrinsic pressures may be exerted on the physician from noninvolved and involved parties in regard to returning an athlete to com- petitive activities.

The decision to return an athlete to a par- ticular sport should be based on the mechanism of injury, objective anatomical injury (as demonstrated by clinical ex- amination and radiographic evaluation) and an athlete's re- covery response.

Because of the potential for significant cata- strophic sequela from premature or inappropriate resumption of athletic participation, an understanding of the natural his- tory of specific clinical syndromes and inherent risk factors should be familiar to the treating physician.
At the time of cervical injury, the patient should be re- moved from the sport in which he or she is participating [21]. A complete history and physical examination should be performed at the scene of the injury.

After an episode of transient quadraparesis, the athlete should be removed from the sport for at least that particular event, even if a full recovery occurs during the sporting ac- tivity.

If symptoms are momentary or resolve, a complete neurologic and radiographic examination should be per- formed on a timely basis and repeated as necessary if any persistent motor or sensory deficits are present. If the patient complains of significant neck stiffness, has worsening complaints of neck pain with axial head compression or if symptoms of neck pain persist, the player has a fracture un- til proven otherwise.

If neurologic complaints persist at the time of evaluation, then a cervical orthosis should be ap- plied. Special precautions should be taken in helmeted ath- letes (removal of shoulder pads and helmet at the same time) to avoid inadvertent cervical manipulation.

In the set- ting of a neurological deficit the patient should be expedi- tiously taken to a medical facility for medical treatment and appropriate imaging studies.

In the setting of stinger, the patient is allowed to return to play at that sporting event if he or she has complete resolu- tion of symptoms, return-to-baseline range of motion of the cervical spine as well as return-to-baseline strength profile.

If the athlete has a significant and sustained stinger (other than brief or momentary) for the first time, he or she should not be allowed to participate in the current athletic contest until an MRI is performed to rule out a significant disc her- niation or other structural abnormality. In the setting of per- sistent symptoms, cervical radiographs (anteroposterior; lat- eral, C1 to T1; and odontoid views) and a cervical MRI should be performed. If suspicion exists for an occult cervi- cal spine fracture, a CT scan or single-photon emission com- puted tomography (SPECT) scan may facilitate diagnosis.

Summarizing the literature as well as the authors' clini- cal experience, the authors recommend the following re- turn-to-play criteria provided below. These are only guide- lines, however, and should be modified appropriately depending on the clinical scenario.
1. Clinical history or physical examination findings of cervical myelopathy.
2. Presence of cervical spinal cord abnormality noted on MRI.
3. History of a C1-2 cervical fusion.
4. Asymptomatic ligamentous laxity (ie, greater than
11 degrees of kyphotic deformity as compared with the cephalad or caudal vertebral functional spinal unit or more than 3.5 mm movement on lateral flex- ion extension films.
5. Radiographic evidence of C1-2 hypermobility with an anterior dens interval of 4 mm or greater.
6. C1-2 rotatory fixation.
7. Evidence of a spear tackler spine on radiographic
8. Radiographic evidence of a distraction/extension
cervical spine injury.
9. A multiple-level Klippel-Feil deformity.
10. Radiographic evidence (ie, MRI) of basilar invagi- nation.
11. MRI evidence of Arnold-Chiari malformation.
12. Radiographic evidence of ankylosing spondylitis or
diffuse idiopathic skeletal hyperostosis.
13. More than two previous episodes of transient quadri-
plegia or quadriparesis.
14. Status after cervical laminectomy.
15. A healed subaxial spine fracture with evidence of a
kyphotic sagittal plane or coronal plane abnormality. 16. Radiographic evidence of significant residual cord encroachment after a healed stable subaxial spine
17. Continued cervical neck discomfort or any evidence
of a neurologic deficit or decreased range of motion
from baseline after a cervical spine injury.
18. Symptomatic disc herniation.
19. Clinical or radiographic evidence of rheumatoid ar-
20. Three-level cervical spine fusion