Plyometrics and PNF Training

PlyometricsObjective:

To improve speed, power, elastic strength

Athletes involved:Sprinters, games players (basketball)

Typical exercises:Jumping, bounding, medicine ball work

Basic theoryFirst 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 contractionThe muscle shortening on the upward phase

Example1. Tricep lengthens as landing happens (eccentric contraction)

2. Upward phase of movement – tricep shortening (concentric contraction)

Three phases of plyometricsThe 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

Use the example below to demonstrate your understanding of plyometrics

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)

AdaptationsTraining using plyometrics leads to:

Increased contractility of the fibreIncreased elasticity – muscle contracts with

more power (ELASTIC STRENGTH)

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 CNSMessage sent to increase the concentric

contractionTo prevent muscle from being over lengthened,

over stretched and therefore injured.CALLED STRETCH REFLEXThis causes increase in the elasticity and

contraction force. ELASTIC ENERGY IS STORED.

PNF TrainingProprioreceptive Neuromuscular Facilitation

ObjectiveTo improve flexibility

Athletes involved:Elite performers

Typical exercises:Hamstring stretch, pectoral stretch

Example – hamstring stretchPassive 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.

Example – hamstring stretch1. Passive stretch

2. Performer applies force back, isometric contraction (stays same length) in the agonist, helper prevents movement. Hold for about 8 seconds.

3. Relax

4. 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.

Use the example below to demonstrate your understanding of PNF.

Use the example below to demonstrate your understanding of PNF.

1. Passive stretch

2. Performer applies force back, isometric contraction (stays same length), helper prevents movement. Hold for about 8 seconds.

3. 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.

AdaptationsTraining 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

TheoryPNF stretching also triggers the GOLGI TENDON

ORGAN which is encased in the tendonJob is to prevent overstretchingIf 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.