Contraction types and the stretch-shortening cycle

Overview

Isotonic, concentric, eccentric and isometric contractions in a block landing, a biceps curl and a press-up, the stretch-shortening cycle and its three phases, the amortisation phase, elastic energy, the stretch reflex, countermovement jumps and the triple jump.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   Define an isotonic contraction.

   Model answer

   An isotonic contraction changes the length of a muscle while it produces tension, so the joint moves. Concentric and eccentric contractions are the two kinds.

2. 2

   Define a concentric contraction.

   Model answer

   A concentric contraction shortens a muscle while it is under tension. The two ends of the muscle move closer together.

3. 3

   Define an eccentric contraction.

   Model answer

   An eccentric contraction lengthens a muscle while it is under tension. The muscle acts as a brake, controlling a movement against gravity or momentum.

4. 4

   Define an isometric contraction.

   Model answer

   An isometric contraction develops tension without the muscle changing length. The joint stays still, so the contraction provides stability rather than movement.

5. 5

   Which contraction does the quadriceps group perform as a volleyball player lands from a block?

   Model answer

   The quadriceps group contracts eccentrically. The lengthening muscle controls knee flexion and absorbs the force of landing.

6. 6

   Which contraction does the biceps brachii perform as a weight is lowered in a biceps curl?

   Model answer

   The biceps brachii contracts eccentrically to control the weight on the way down. Gravity, not the triceps, extends the elbow.

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