PLYOMETRICS

1. PLYOMETRICS Raoul Hiranicscs

2. Plyometrics: • “Plio” = More • “Metric” = Measure Is a type of exercise that uses explosive movements to develop muscularpower, the ability to generate a large amount of force quickly.

3. Mechanism in Plyometrics • Musculotendinous component: • If the muscle is lengthened (eccentric contraction) just prior to the contraction, it will produce greater force through the storage of elastic energy • This effect requires that the transition time between eccentric contraction and concentric contraction (amortisation phase) be very short. • The process is frequently referred to as the "stretch shortening cycle", and is one of the underlying mechanisms of plyometric training.

4. Plyometric training conditions the neurons to contract with a single powerful surge rather than several disorganized contractions • Therefore, a plyometric exercise involves: • 1) An eccentric contraction • 2) A brief amortisation phase (no change in muscle length) • 3) A short concentric contraction delivering maximum force in a short period of time

5. As guidelines, athletes over 120kg in weight should not perform depth jumps from heights exceeding 50cm. Similarly, depth jumps should not be performed until a player can perform a freeweight squat exercise with a mass that is 1.5 times his bodyweight.

6. Planning a Plyometric Session • Begin with exercises that are fast, explosive and designed for developing elastic strength (low hurdle jumps; low drop jumps) • Work through exercises that develop concentric strength (standing long jump; high hurdle jumps) • Finish with training for eccentric strength (higher drop jumps)

7. Where to do it and what to wear • For bounding exercises use surfaces such as grass or resilient surfaces. • Avoid cement floors because there is no cushioning. • Choose well-cushioned shoes that are stable and can absorb some of the inevitable impact.

8. How many? • Keep the volume low and the intensity high • Youth Athletes 20 – 150 Ground Contacts Per Session, split the work into sets with ample recovery in between. • Keep the reps low per set For horizontal movements • Speed/Power = 50 yards or less per repetition • Power/Endurance = 50 – 200 yards per repetition. Monitor your athlete’s rest intervals in order to achieve the session goals

9. Safety Considerations • Good levels of physical strength, flexibility and proprioception should be achieved before commencement of plyometric training. • Never do these exercises while lifting heavy loads. • Generally it is preferred that bodyweight be used. The focus should be on a ballistic rebound action. • Too much weight will slow the athlete’s response, thus negating any positive effects.

10. Age - low-intensity and low-volume only for athletes under the age of 13 or for athletes who squat less than 1.5 times their bodyweight. Surface- some degree of softness is needed. Gymnastics mats are ideal, grass is suitable. Hard surfaces such as concrete should never be used. Footwear - must have adequate cushioning and be well fitting. Bodyweight - athletes who are over 240 pounds should be very careful and low-intensity plyometric exercises should be selected. Technique - most importantly, a participant must be instructed on proper technique before commencing any plyometric exercise. They should be well rested and free of injury in any of the limbs to be exercised.

11. SUMMARY • Plyometrics has an important role in sports performance, injury rehabilitation and for injury prevention, thus it can be used as an effective measure in physiotherapy as well.