Plyometrics and PNF Training

1. Plyometrics and PNF Training

2. Plyometrics • Objective: • To improve speed, power, elastic strength • Athletes involved: • Sprinters, games players (basketball) • Typical exercises: • Jumping, bounding, medicine ball work

3. Basic theory • First an eccentric contraction takes place • E.g. breaking action of the quadriceps when landing, slows down the movement, lengthening of muscle. • Followed by a concentric contraction • The muscle shortening on the upward phase

4. Example 1. Tricep lengthens as landing happens (eccentric contraction) 2. Upward phase of movement – tricep shortening (concentric contraction)

5. Three phases of plyometrics • The eccentric phase, or landing phase, where the agonist muscles are contracting eccentrically to control movement (elatsic energy is stored) • The amortisation phase, or transition phase, which is the time between eccentric and concentric contractions (shorter the more explosive the movement) • The concentric phase, which is the jumping phase, when the agonist muscles contract concentrically

6. Use the example below to demonstrate your understanding of plyometrics

7. Use the example below to demonstrate your understanding of plyometrics 1. Quadricep lengthens as landing happens (eccentric contraction) 2. Upward phase of movement – quads shortening (concentric contraction)

8. Adaptations • Training using plyometrics leads to: • Increased contractility of the fibre • Increased elasticity – muscle contracts with more power (ELASTIC STRENGTH)

9. How does this work? • Around the myofibrils there are muscle spindles (propriorecptors). • The muscle spindle’s job is to relay information to the brain on the condition of the muscle. • As the muscle rapidly lengthens( contracts) the spindles send message to CNS • Message sent to increase the concentric contraction • To prevent muscle from being over lengthened, over stretched and therefore injured. • CALLED STRETCH REFLEX • This causes increase in the elasticity and contraction force. ELASTIC ENERGY IS STORED.

10. PNF Training • Proprioreceptive Neuromuscular Facilitation • Objective • To improve flexibility • Athletes involved: • Elite performers • Typical exercises: • Hamstring stretch, pectoral stretch

11. Example – hamstring stretch Passive stretch due to helper. The helper produces force by pushing on the foot. Causing a stretch in the hamstring, lengthening As the muscle lengthens the muscle spindles work causing stretch reflex.

12. Example – hamstring stretch Passive stretch Performer applies force back,isometric contraction (stays same length) in the agonist, helper prevents movement. Hold for about 8 seconds. Relax Leg stretched AGAIN (another isometric contraction) causing leg to stretch in a greater range of movement. Due to muscle spindles delaying sending message to CNS which switches off stretch reflex.

13. Use the example below to demonstrate your understanding of PNF.

14. Use the example below to demonstrate your understanding of PNF. Passive stretch Performer applies force back, isometric contraction (stays same length), helper prevents movement. Hold for about 8 seconds. Pectorals stretched AGAIN (another isometric contraction) causing arms to stretch in a greater range of movement. Due to muscle spindles delaying sending message to CNS which switches off stretch reflex.

15. Adaptations • Training using PNF leads to: • Muscle AND connective tissue (tendons and ligaments) become more flexible (move through a greater range of movement). The most common PNF technique is the CRAC Technique: contract – relax , antagonist - contract

16. Theory • PNF stretching also triggers the GOLGI TENDON ORGAN which is encased in the tendon • Job is to prevent overstretching • If the muscle is under too much pressure during isometrical contraction, the GTO relaxes the muscle to avoid tearing. • GTO override the stretch reflex allowing the relaxation to be extended. • The athlete practices engaging the GTO during exercise and then follows with a deep stretch pushing the muscle beyond its normal range.