Plyometrics

KIN 425 Concepts of Strength & Conditioning

Plyometrics:

· Activities that enable a muscle to reach maximal force in the shortest possible time

· Plyometric exercise is a quick, powerful movement using a pre-stretch, or countermovement, that involves the stretch-shortening cycle (SSC).

· When used correctly, plyometric training has consistently been shown to improve the production of muscle force and power.

Muscle Spindles:

· Proprioceptive organs that are sensitive to the rate and magnitude of a stretch; when a quick stretch is detected, muscular activity reflexively increases. This reflexive response pontentiates, or increases, the activity in the agonist muscle, thereby increasing the force the muscle produces.

Stretch-Shortening Cycle (SSC):

· The basis of plyometric exercise. A rapid eccentric muscle action stimulates the stretch reflex, which increases the force produced during the subsequent concentric action.

Stretch Shortening Cycle

Phase	Action	Physiological Even
I. Eccentric	Stretch of Agonist Muscle	-Muscle spindles stimulated -Elastic energy stored
II. Amortization	Very Slight pause between phases I&II	-Transference of motor nerve signals (in to motor neurons and out to agonist muscle group
III. Concentric	Rapid shortening of Agonist muscle fibers	-Elastic energy is released and turned into kinetic energy -Motor neurons stimulate the agonist muscle group.

Progression of lower-body Plyometric Drills

1. Jumps in place [vertical jump]

2. Standing jumps [broad jump]

3. Multiple hops and jumps [hurdle hops]

4. Bounds [sprint bounding]

5. Box Drills

6. Depth Jumps

Rest:

· Complete and adequate rest is required between sets of plyometric drills

Surface

· To prevent injuries, the landing surface used for lower-body plyos should possess shock-absorbing properties.

Footwear

· Footwear with good ankle and arch support, good lateral stability; and a non-slip sole is recommended.