LEWIS: Plyometrics Flashcards Preview

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Flashcards in LEWIS: Plyometrics Deck (28):

Plyometrics involves high intensity, explosive

Muscular contractions


Type of training designed to improve



Plyometric exercises involve bounding, jumping or hopping to make muscle groups work

Eccentrically before a powerful concentric contraction


focuses on engaging the

Stretch reflex


The stretch reflex is a protective mechanism that

Prohibits over stretching of muscle fibres


Any tendency to over stretch is detected by specialised receptors in muscles called

Muscle spindles


When muscle spindles are suddenly activated, a nerve impulse is sent to the spinal chord which results in the immediate contraction of the

Muscle being over stretched


Eccentric contractions occur when the muscle lengthens as it develops tension - these contractions occur during

Downward movements


Concentric = shortening
Occurs during

Upward movements


Plyometrics contraction involves an

Initial rapid eccentric movement
An explosive concentric movement


A muscle that is eccentrically stretched before a concentric contraction will

Contract more forcefully and more rapidly


Plyometrics works as a form of power training because, when a quick stretch is detected in the muscles, an involuntary protective stretch reflex occurs to prevent over stretch and injury - the stretch reflex increases the activity in the muscle undergoing the stretch allowing it to

Act more forcefully

Result = powerful braking effect and the potential for a powerful concentric muscle action


If the concentric muscle action does not occur immediately after the pre-stretch, the potential energy produced by the stretch reflex response is



The sequence of the 3 phases is called the

Stretch-shortening cycle


3 phases:

1)Eccentric muscle action - elastic (potential) energy is generated and stored in the elastic tissues of the muscle

2)Amortisation - short time between end of eccentric and start of concentric
The shorter this phase the more powerful the subsequent muscle contraction Will be

3)concentric muscle action/Actual muscle contraction, involves an upward concentric contraction which results in improved muscular performance


By utilising the stretch-shortening cycle, movements can be made

more powerful and explosive


Questioned suitability because there is a

Risk of injury


As a precaution to reduce injury it is suggested that performers attempting to introduce Plyometrics do so with a

substantial strength-training background


Injuries are more likely to occur if there are

Depth jumps from TOO great a height
Improper landing
Inappropriate landing surface


Landing surface=important
Should possess adequate

Shock-absorbing properties, e.g. Grass, rubber mats or suspended floor


Plyometrics can improve performance in

Vertical jumping
Long jumping
Sprint cycling


plyometric training uses muscles' elastic properties and proprioceptors (muscle spindles and GTO) to generate maximum force by:

increasing the recruitment of muscle in a minimal amount of time


The eccentric contraction immediately preceding a concentric contraction significantly increases the force generated concentrically as a result of the storage of elastic potential energy. This extra energy is released as

kinetic energy during the concentric phase


3 mechanism by which plyometric training improves performance:

-Enhanced muscle spindle activity
-Desensitisation of the GTO
-Enhanced neuromuscular efficiency


Enhanced muscle spindle activity: (SET THE MUSCLE TO A PRESET LENGTH) when muscle spindles are stretched the muscle spindles are also stretched. This causes the spindles to send nerve impulses that result in reflex contraction of the stretched muscle. This reflex enables the muscle to

rapidly return to its preset length


Desensitisation of the GTO: Repeated plyometric exercises desensitise the GTO by increasing the degree of stimulation needed for the GTO to inhibit muscle contraction. This means that:

the muscle can produce more force


Enhanced neuromuscular efficiency: May promote better coordination of contracting agonists and synergists, thus improving the efficiency of the CNS, Making use of the stretch reflex, inhibiting the GTO and enhancing the ability of the nervous system to react to the lengthening muscle optimises the

force produced by the concentric contraction


Plyometrics improves jumping ability, running economy and power output but not:

improved strength