Which statement best describes isotonic contractions?

Which statement best describes isotonic contractions?

• A. The joint angle remains fixed during contraction
• B. The muscle length increases during contraction
• C. The muscle length changes as it contracts to cause movements
• D. The muscle length remains constant during contraction

Answer: (C)

Isotonic contractions are when a muscle changes length as it contracts to cause movement at a joint. This means the muscle can shorten (concentric) to lift or move a load, or lengthen (eccentric) while controlling a descent. So the idea that the muscle length changes as it contracts to produce movement best describes isotonic contractions. In contrast, if the joint angle doesn’t move, that’s an isometric contraction, where the muscle length stays the same.

Isotonic contractions are when a muscle changes length as it contracts to cause movement at a joint. This means the muscle can shorten (concentric) to lift or move a load, or lengthen (eccentric) while controlling a descent. So the idea that the muscle length changes as it contracts to produce movement best describes isotonic contractions. In contrast, if the joint angle doesn’t move, that’s an isometric contraction, where the muscle length stays the same.