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Biomechanics Lecture 13 - Major Events of Muscle Function
Terms in this set (50)
Major events of contact period -
Deceleration of ankle joint
plantarflexion at heel strike.
Loading of the forefoot from lateral to medial.
Deceleration of subtalar joint pronation and internal leg rotation.
Deceleration of anterior momentum of the leg.
____ ____ muscle with assistance
from the ____ ____ ____ muscle decelerate ankle joint plantarflexion at heel strike.
extensor hallucis longus
DECELERATION OF ANKLE JOINT PLANTARFLEXION
Avoids considerable trauma to the _____ .
Anterior tibial dysfunction results in _____ at heel contact.
_ _ _ dysfunction, no appreciable symptomology. Person with _____ _____ muscle dysfunction will shorten stride to slow down gait in order to minimize trauma due to foot slap.
Anterior tibial also (inverts/everts) the forefoot around the
Only the _____ side of the forefoot makes contact with the ground initially because of the anterior tibial muscle.
____ ____ muscle relaxes allowing GRF's to evert the forefoot smoothly, loading from lateral to medial.
The leg is internally rotating and the STJ pronating during contact period.
The ____ ____ muscle is the first
muscle to decelerate STJ pronation and internal leg rotation.
When the forefoot contacts the ground, the _____ muscle then joins the posterior tibial muscle in deceleration.
_ _ _ and _____ muscle begin contracting during the last half of the contact period to decelerate STJ pronation.
_ _ _ helps to decelerate internal
(TQ) The _____ muscle decelerates internal rotation of the
to prevent _____ from developing at the knee joint.
The _ _ _ muscle contracts at the
end of the contact period
to assist in stopping STJ pronation and internal leg rotation.
_____ _____ muscle exerts the strongest and longest deceleration force during the contact period.
_____ _____ muscle function
will result in severe pronation at heel strike. Also known as _____ _____.
(TQ) Posterior tibial muscle function loss can result in severe _____ forefoot compared to rearfoot because we lose (medial/lateral) pull and the _____ _____ muscle has a greater mechanical advantage to pull (medailly/laterally).
The _____ _____ muscle is the primary decelerator of anterior momentum of the tibia during the last half of the contact period.
The _____ muscle is the first muscle to assist the PT in decelerating anterior momentum of the tibia, followed by the _ _ _, and lastly at the end of contact period by the _ _ _.
At the same time the _____ muscle keeps tension on the knee in flexion, preventing the knee from hyperextending as the tibia is decelerated.
Major events of midstance period -
Acceleration of subtalar joint supination and external leg rotation.
Deceleration of the forward momentum of the tibia and extension of the knee.
Stabilization of the bones of the lesser tarsus.
Stabilization of the bones of the metatarsus.
Posterior calf muscles are agonists
and accelerate STJ _____ and _____ leg rotation.
The posterior calf muscles have been contracting since contact period. (PT, soleus, FDL, FHL)
The _____ muscle accelerates external rotation of the femur.
During the last half of the midstance period the _____ _____ and _____ _____ muscles function as antagonists to the calf muscles.
_____ _____ is a strong pronator of the STJ.
The _____ control the rate and extent of STJ supination during midstance.
Ankle joint _____ seen throughout midstance period.
Muscles that decelerate the forward momentum of the tibia and knee extension are the:
posterior tibial, soleus, long digital flexors (FHL, FDL), with some help from the peroneus longus.
The _____ maintains flexion
tension at the knee to prevent
uncontrolled extension at the knee.
Prevent the knee from snapping into hyperextension.
Paralyzed _____ - knee snaps into hyperextension during midstance.
STABILIZATION OF THE BONES
OF THE LESSER TARSUS
Early in midstance - _____, _____ _____, _____ _____, and _____ _____ muscles are responsible.
The _____ muscle maintains sagittal plane stability of the
so it can serve as a pulley to the peroneus longus. _____ _____ pulls the 1st ray laterally against the lesser tarsus.
Posterior tibial pulls the lesser tarsal bones _____.
Together the PL and PT compress the lesser tarsus in the _____ plane
producing medial - lateral stability.
PB and PL counteract the _ _ to maintain transverse plane stability of the lesser tarsus during the stance phase of gait.
PL and PT muscles exert a _____ force on the lesser tarsal bones they attach to providing sagittal plane compression, stabilizing the
lesser tarsal bones _____ against each other and against the talus and calcaneus.
(Late in midstance the posterior stabilization is assisted by the abductor hallucis, short digital flexors (FHB, FDB), quadratus plantae, and abductor digiti quinti.)
Weakness or paralysis of the PT or
spasm of the PB result in an unopposed _____ force on the midfoot.
Causes STJ pronation to achieve
abduction of the forefoot beyond locking position, resulting in entire foot pronated or peroneal _____ _____.
Weakness of paralysis of the PB or spasm of the PT causes forefoot to be _____ by the PT, _____ the STJ first and the MTJ second.
Results in a ____ _____ foot.
Spasm of the PL muscle the _____ 1st ray.
The MTJ _____ about the LMTJ axis, eventually the STJ _____ to compensate for the everting forefoot.
Will also eventually result in a moderate pes cavus deformity.
Metatarsals must become stable before they can bear weight for propulsion.
Major function of _____ _____ muscles during the last half of the midstance period is to provide tension forces to stabilize the metatarsus and lesser tarsus transversely and posteriorly against each other.
STABILIZATION OF THE METATARSUS - 2ND, 3RD, 4TH RAYS:
Central three rays have axis of motion lying in the transverse and frontal planes, so motion occurs in the ____ plane only.
When the rearfoot inverts with STJ
supination the forefoot inverts also,
inverting the axis of the 3 central rays to the ground as the STJ supinates past neutral at the end of midstance.
During the first half of midstance skeletal integrity is maintained by the _ _ _ and _ _ muscles. These muscles resist excessive dorsiflexion of mets 2, 3, and 4.
(TQ) During the last half of midstance the FDL and PT are assisted in stabilizing mets 2, 3, and 4 by the ____ ____ and the _____ muscles.
STABILIZATION OF THE
METATARSUS - 1ST RAY:
The _____ _____ muscle stabilizes the first ray at its base plantarly, posteriorly, and laterally using
the cuboid as a pulley.
PL plantar force on the first ray is
by STJ _____ and
by STJ _____.
(Normally STJ supination results in a stable first ray due to PL functioning to stabilize the first ray.)
Major events of the propulsive period -
Heel lift initiating propulsion.
Ankle joint plantarflexion.
Transverse stabilization of the
Medial transference of body weight.
Propulsive function of the lesser digits.
Propulsive function of the hallux.
Combination of three factors:
1. forward momentum of the body,
2. deceleration of the tibia, and
3. active knee flexion.
At the start of propulsion the trunk is (in front of/above/behind) the foot.
The body is falling forward over the weight bearing foot.
in front of
As the trunk, thigh, and leg fall forward the _____ muscles decelerate the tibia during midstance.
The tibia still moves forward but at a slower rate than does the trunk and thigh. Results in knee extension force.
Just before heel lift the _____ contracts, stopping knee extension and beginning knee flexion.
The femur and tibia still move forward as the trunk continues forward due to momentum.
Net effect of knee flexion is heel lift.
Heel lift also occurs because the _____ muscles decelerating the tibia also decelerate ankle joint _____, momentum forces heel off the ground.
ANKLE JOINT PLANTARFLEXION:
Shortly after heel off, ankle joint dorsiflexion is stopped due to weight no longer passing through the heel.
Ankle joint plantarflexion is started by the gastrocnemius, soleus, FDL, FHL, PL, and PT in the early stage of propulsion.
(TQ) During the last half of propulsion the _ _ _ and _ _ _ only are responsible for plantarflexion. _ _ _ plantarflexes ankle joint until almost toe off.
OF THE METATARSAL HEADS:
_____ ____ muscle = only muscle having the requirements to stabilize the forefoot during propulsion transversely.
Forces present on the forefoot include vertical GRF's, anterior shear, and torque exerted on the ball of the foot.
Forces would cause splaying of the forefoot transversely if not resisted.
MEDIAL TRANSFER OF BODY
_____ ______ and _____ _____ are the primary muscles responsible for lifting the lateral side of the forefoot to transfer weight from lateral to medial.
_____ loses its stabilizing function on the cuboid after heel lift. So as peroneus longus contracts it lifts the cuboid while the peroneus brevis lifts the lateral side of the foot.
PROPULSIVE FUNCTION OF THE LESSER DIGITS
Digits must be _____ as rigid beams to be stabilized during
The _____ muscles along with the long and short digital _____ are responsible for extension of the digits creating a rigid beam of the digits for propulsion.
STABILIZATION OF THE
Factors that influence the stability of the hallux-
Stability and plantarflexion of the first ray.
Normal sesamoid function
Normal strength and function of
musculature involved in stability of the hallux and first ray.
GRF's at heel off force the hallux to _____, which _____ the first ray.
The _____ _____ muscle plantarflexes the first ray at this time helping to stabilize the
first met head against the sesamoids.
_ _ stabilizes the base of the first ray in plantar, posterior, and lateral directions.
Extensors - The _ _ _ fires early in
midstance and provides posterior and dorsiflexion stability to the hallux.
_ _ _ fires in the final moments of
propulsion so it is mostly a swing phase muscle.
GRF's mostly responsible for dorsal stability of the hallux.
The _ _ _ and _ _ _ are primarily
responsible for plantar stabilization of the hallux with the help of the
sesamoids acting as pulleys.
Adductor and abductor hallucis
muscles primarily stabilize in the
transverse plane. Also stabilize the
SWING PHASE MUSCLE
FUNCTION OF THE FOOT:
Most muscle activity is at the beginning or end of swing phase.
Muscle activity reduced during the
middle of swing phase.
At the start of swing phase muscles accelerate the foot.
The _____ _____ muscle initiates swing phase by supinating the LMTJ axis, then it dorsiflexes and inverts the first ray.
EHL neutral dorsiflexor of the foot. (very strong)
EDL and peroneus tertius are weak ankle joint dorsiflexors and at the same time pronators of the STJ.
By dorsiflexing the first ray we cause _____ of the hallux.
Net effect is to dorsiflex the foot at the ankle and to pronate the subtalar joint out of its supinated position and into a slightly pronated position during early
Anterior tibial, long extensors (EDL, EHL), and peroneus tertius contract toward the end of swing phase, _____ the forefoot about the LMTJ axis and slightly supinating the subtalar joint immediately before heel strike.
Weakness of these muscles results in foot drop or slap occurring at contact period.
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