chapter 9 Plyometrics Plyometrics Quick movement of eccentric

chapter 9 Plyometrics

Plyometrics • = Quick movement of eccentric activity rapidly followed by a burst of concentric activity to produce a powerful movement • Purpose: increase power of movements Plio = more Metric = measure

Figure 9. 1

Mechanical Components • Muscle lengthening increases elastic tension of noncontractile tissue stored elastic (potential) energy. • If immediately followed by a rapid concentric contraction, release of elastic energy contributes to total muscle output.

Neurological Components • Muscle stretch (eccentric lengthening) stimulates the muscle spindle to create a reflex shortening (concentric). • Movement must occur rapidly for the stretch reflex to occur.

Influential Factors • • Strength Flexibility Speed of movement Efficiency of movement (coordination)

Plyometric Phases: Stretch-Shortening Cycle 1. Eccentric phase – – – Muscle lengthens to take up slack and stretch elastic components. “Sets” the muscle. Stores potential energy as elastic energy. Muscle spindle responds to a rapid stretch and accommodates to a slow stretch. Best with rapid eccentric movement in a partial range of motion. (continued)

Plyometric Phases: Stretch. Shortening Cycle (continued) 2. Amortization phase – – – Must immediately follow the eccentric phase = Time it takes to transfer from eccentric to concentric motion Too much time: potential energy absorbed and dispersed, and spindle reflex overridden by cognitive functions (continued)

Plyometric Phases: Stretch. Shortening Cycle (continued) 3. Concentric phase – Stretch reflex causes increased muscle activity. – Stored (potential) energy is released to increase output. – The combined result is greater muscle performance.

Pre-Plyometric Considerations • Plyometrics is used in therex near the end of the program. • Used with patients returning to power-based sports: basketball, volleyball, gymnastics, track and field, softball, baseball, skating, swimming, soccer, football • Serve as a bridge between therex and sportspecific activities

Plyometric Program Design Mode of training: based on body part Lower-body plyometrics – – – Jumps in place Standing jumps Multiple hops and jumps Bounds Box drills Depth jumps (continued)

Plyometric Program Design (continued) Upper-body plyometrics – Medicine-ball throws – Medicine-ball catches – Push-ups Trunk plyometrics – Medicine-ball sit-ups – Plyometric sit-ups (continued)

Plyometric Program Design (continued) • Intensity: stress of the activity • Volume: – Lower extremity: number of foot contacts – Upper extremity: reps and sets or number of throws – Beginner: 80 -100/session – Intermediate: 100 -120/session – Advanced: 120 -140/session • Recovery: between reps = 5 -10 s; between sets = 2 -3 min • Frequency: once a week to three times a week (QW – TIW)

Program Considerations • • Age: <16 years Weight: >220 pounds Competitive level Surface: not too hard, not too soft Footwear: stable yet absorbing Progression: allow for overload adaptations Goals based on individual needs

Precautions • • Time: early in the session Delayed-onset muscle soreness Proper supervision Depth jumps – Max = 48 in. – Range = 16 to 42 in. – Norm = 30 to 32 in. (if >220 lb, range = 20 to 30 in. ) • Contraindications – Acute inflammation – Post-op – Instability

Exercise Progression • Beginning stages – Double-leg takeoffs – Increasing difficulty levels dependent on athletic level, learning aptitude • With increased mastery, amplitude increases • Consistent emphasis – Coordination – Correct movement and motor patterns

Exercise Techniques • Landing exercises – To teach proper foot strike – Use of ankle, knee, and hip to absorb shock – Correct body alignment • Stabilization jumps – To reinforce correct landing technique – Raise levels of eccentric and stabilization strength – Same as landing exercises, but landing position is held 5 s before next jump (continued)

Exercise Techniques (continued) • Jumping up – To teach takeoff action and arm use – For jump on box: Emphasize arm swing, Jump up with leg tuck • In-place bouncing movements – For quick reaction off ground and vertical displacement – Tuck jump, scissors jump, increasing vertical jump (continued)

Exercise Techniques (continued) • Short jumps – To teach horizontal displacement of center of gravity – Two-foot takeoffs multiple-step takeoffs, power skipping • Long jumps – To add more horizontal velocity – Leg bounding, bounding hops

Exercise Techniques (continued) • Shock jumps – To raise explosive power to highest levels – Impose high neural demand – Advanced form of training—require a large training base – Jump boxes, rebound hurdles

Equipment • Boxes: 16 in. to 48 in. (non-slip surfaces on floor, boxes) • Cones • Hurdles • Medicine balls • Other equipment

Precautions • Increase one factor q 3 d, especially in early phases. • Provide constructive cues to correct performance. • Avoid pain and swelling. • Understand tissue integrity: Be alert to progression tolerance. • Understand patient’s confidence level.

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