Contraction modes

Concentric, eccentric, isometric, plyometric and isokinetic: what the muscle does and what it costs.

The outline, topic by topic

Each topic is weighted the way the exam weighs it.

Concentric: what is it?
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The muscle shortens while producing force.
Lifting a load.
After a long trail descent, the thighs are very sore. Why?
- Eccentric work caused micro-damage
- Lactic acid built up
- Isometric work tires the heart
- Type I fibres lacked oxygen
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Eccentric work caused micro-damage
Braking while lengthening damages fibres more.
Eccentric: what is it?
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The muscle lengthens while producing force, to brake.
It produces more force than concentric work.
Why do we jump higher with a countermovement?
- The muscle gets time to rest before the push
- The stretch stores elastic energy given back in the push
- The countermovement lightens the body at take-off
- The dip shortens the extensors before the push
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The stretch stores elastic energy given back in the push
That is the stretch-shortening cycle: elastic energy and the stretch reflex strengthen the push that follows.
Isometric: what is it?
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The muscle produces force without changing length.
A plank is a typical example.