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Terms in this set (69)

o In order to execute techniques, athletes must skillfully apply force - mass*acceleration

o Impulse
- The change in momentum from a force, measured as the product of force *time
- A basic objective of training is to move the force time curve upward and to the left, generating a greater impulse and momentum during limited time which force is applied

o Power
- The rate of doing work, force * velocity
- High power outputs are required to rapidly accelerate, decelerate, or achieve high velocities

o Athletes skillfully apply forces when executing movement techniques, because of time and velocity constraints a technique can be characterized in terms of task specific impulse and power. The ability to achieve high movement velocities and accelerations involve high RFD as well as force application across a range of power outputs and muscle actions.

o Practical Implications
- Functional vs. Simple Movements
• Speed in complex, functional movements involves an interplay of neuromuscular, mechanical, and energetic factors
• Speed in complex movements' correlates poorly with speed in unresisted, elementary actions.
• Many functional tasks begin with a prep counter movement and utilize the SSC.

o SSC: eccentric contraction coupling phenomenon in which the muscle tendon complexes are rapidly and forcibly lengthened or stretch loaded and immediately shortened in a reactive or elastic manner; springlike prep counter movement of many functional tasks.

• Training activities aimed at improving SSC performance should fulfill two criteria:
o Involve skillful multijoint movements that transmit forces through the kinetic chain and exploit elastic reflexive mechanisms.
o In order to manage fatigue and emphasize work quality and technique, they should be structured around brief work bouts or clusters separated by frequent rest pauses.

• Reactive ability: a characteristic of explosive strength exhibited in SSC actions that can be improved through explosive training.

• Reaction time: relatively untrainable and correlates poorly with movement action time or performance in many explosive events.

- Aerobic endurance vs. power sports
• Explosive strength qualities also play an important role in aerobic endurance activities

o Ground contact times at intermediate running speeds are longer than those at top speed but significantly shorter than required for max force development

o Power, impulse, and reactive ability are important determinants of running performance over any distance.

o SSC actions are prevalent in athletic tasks. The target activity's movement mechanics have important implication in training and should be addressed in the task analysis
o Stride frequency tends to vary among individuals and generally is more trainable than stride length

o Sprinting Performance and Stride Analysis
- Linear sprinting involves a series of subtasks - the start, acceleration, and max velocity
- Though the movement mechanics of these two subtasks are distinct, both are characterized by two phases
• Flight
• Support
- Running is a ballistic mode of locomotion alternating phases of flightand single leg support.
- Following is a summary of key muscular requirements in max velocity sprinting:
• As the recovery leg swings forward, eccentric knee flexor activity controls its forward momentum and helps prepare for an efficient touchdown
• During ground support, the high moment at the ankle joint indicates the importance of the plantar flexors.
• Effort during the late support phase neither is essential to sprinting efficiency nor poses a high risk of injury.

o Training goals
- Minimize braking forces at ground contact by maximizing the backward velocity of the leg and foot at touchdown and by planting the foot directly beneath the center of gravity
- Emphasize brief ground support times as a means of achieving rapid stride rate
- Emphasize functional training of the hamstring muscle group with respect to its biarticular structure and dual mode during late recovery
- Eccentric knee flexor strength is the most important aspect limiting recovery of the leg as it swings forward.

o Running speed is the interaction of stride frequency and stride length. The goal of sprinting is to achieve high stride frequency and optimal stride length, with explosive horizontal push off and minimum vertical impulse.
o Athletes collective coordinative abilities
- Adaptive ability: modification of action sequence upon observation or anticipation of novel or changing conditions and situations.
- Balance: static and dynamic equilibrium
- Combinatory equilibrium: coordination of body movements into a given action
- Differentiation: accurate, economical adjustment of body movements and mechanics
- Orientation: spatial and temporal control of body movements
- Reactiveness: quick, well directed response to stimuli
- Rhythm: observation and implementation of dynamic motion pattern, timing, and variation

o Skill Classification
- General vs. special skills
- Closed vs. open skills
- Continuous vs discrete vs serial skills

o Change in velocity
- An Initial speed and direction
- Decrease or increase in speed and redirection of movement
- Final speed and direction

o Locomotion mode
- The specific locomotion modes performed and the movement techniques used to execute them discretely
- The specific sequences in which they are performed and the techniques used to transition between them serially

o Backpedal running is a distinct technique rather than a simple reversal if forward running; Athletes maximal backward running velocities tend to be 60-80 percent of their forward velocities.

o Technical Considerations
- Linear sprinting can be described as a closed serial task
• Velocity: the athlete starts with an initial speed of zero and maximally accelerates forward and achieves maximum speed over a distance with minimum deceleration or redirection.
• Mode: the athlete runs forward by executing a series of discrete subtasks without transitioning to another mode of locomotion
- Certain sprinting mechanics - including body position, visual focus, leg action, arm action and braking mechanics - can be adapted to various multidirectional tasks.
- Considering the forces involved in explosive deceleration and the role of SSC actions in redirection, some principles of plyometric training are also applicable
- Braking mechanics
• Instruct athlete to run forward achieving second gear (1/2 speed) and then decelerate and stop within three steps
• Third gear (3/4 speed) and then decelerate and stop within five steps
• Fourth gear (full speed) and then decelerate and stop within seven steps