A muscle action in which muscle tension supposedly remains constant while the muscle changes its length as it overcomes a constant resistance. Isotonic means equal in tone’ and implies constant force development. However, no dynamic muscle action in sport or exercise performance involves constant force development because of variations in mechanical advantage as a joint angle is changed, as well as differences in maximal force capability of a muscle through its range of length. It has therefore been suggested that the term ‘isotonic’ should not be used in relation to human exercise performance. See also concentric action, eccentric action.
Subjects: Sports and Exercise Medicine.