Which statement best defines isotonic exercise?

• A. Isotonic exercises involve movement with length change in muscles.
• B. Isotonic exercises require holding a position without movement.
• C. Isotonic exercises involve only breathing techniques.
• D. Isotonic exercises involve increasing muscle tension without movement.

Answer: (A)

Isotonic exercise involves movement where the muscles change length as they contract, producing joint motion. This means you actively move a limb or body part against resistance, causing the muscle to shorten (concentric phase) and then lengthen (eccentric phase) through the range of motion. That’s why the description of movement with length change in muscles is the best fit. Other options describe static holds without movement (isometric) or actions that don’t involve a change in muscle length, such as breathing techniques or increasing tension without movement. For example, lifting and lowering a dumbbell illustrates isotonic action because the muscle length changes as you move.