Isotonic Muscle Contraction

contraction of a muscle at unchanging tension, expressed in a decrease in its length and an increase in its transverse section. Purely isotonic muscle contraction is not observed in the body. The movement of an unloaded extremity approaches purely isotonic muscle contraction. By gradually increasing a load to the point where it can no longer be lifted, it is possible to observe all of the steps in the transition from isotonic muscle contraction to isometric muscle contraction.