Which statement best describes isotonic exercise?

• A. Exert resistance against the muscle as it moves through a range of motion.
• B. Involve the joints moving and muscles contracting.
• C. Use muscle tension with little movement.
• D. Aerobic rhythmic activity over extended periods.

Answer: (B)

Isotonic exercise is about dynamic movement where the muscles contract while the joint moves, causing the muscle to change length. The key idea is that the joint produces motion as the muscle shortens or lengthens, such as lifting or lowering a weight through a full range of motion. This distinguishes it from static holds, where the muscle contracts without moving the joint (isometric), or from aerobic activities, which emphasize sustained rhythmic movement rather than a single muscle working through a range. For example, a bicep curl shows isotonic action: the elbow moves and the biceps contract to lift the weight, then lengthen as you lower it.