Plyometrics
 Objective:
 To improve speed, power, elastic strength
 Athletes involved:
 Sprinters, games players (basketball)
 Typical exercises:
 Jumping, bounding, medicine ball work
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
Example
1. Tricep lengthens as
landing happens (eccentric
contraction)
2. Upward phase of
movement – tricep
shortening (concentric
contraction)
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
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)
Adaptations
 Training using plyometrics leads to:
 Increased contractility of the fibre
 Increased elasticity – muscle contracts with more power
(ELASTIC STRENGTH)
How does this work?
 Around the myofibrils there are muscle spindles
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(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.
PNF Training
 Proprioreceptive Neuromuscular Facilitation
 Objective
 To improve flexibility
 Athletes involved:
 Elite performers
 Typical exercises:
 Hamstring stretch, pectoral stretch
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.
Example – hamstring stretch
1. 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.
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
Theory
 PNF stretching also triggers the GOLGI TENDON
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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.