What is an example of an isotonic contraction?

An isotonic contraction occurs when a muscle changes length while producing a constant tension. This type of contraction is characterized by movement—either through shortening (concentric contraction) or lengthening (eccentric contraction) of the muscle. Lifting a weight represents a classic example of an isotonic contraction, as the muscle fibers are actively shortening to lift the load against gravity. During this action, the tension within the muscle remains consistent, but the muscle length changes as it contracts to overcome the resistance of the weight.

In contrast, holding a position is an isometric contraction, where the muscle generates tension without changing length. Squeezing a ball also involves isometric contraction, as the muscle maintains its length while exerting force. Stretching a muscle is related to increasing the length of the muscle fibers without generating muscle tension. All these options reflect different types of muscle contractions but do not exemplify the isotonic contraction as clearly as lifting a weight does.