M1TI Osteopathic Manipulative Medicine (OMM) Practice Test

Isotonic contractions involve changing the length of a muscle while lifting or lowering against a constant load. In this context, the muscle either shortens as it contracts to lift the weight (concentric) or lengthens as it contracts to control or slow the descent (eccentric). Concentric contraction occurs when the muscle brings the attached bone closer, like curling a dumbbell upward. Eccentric contraction happens when the muscle maintains control as the limb moves away from the shortened position, such as lowering the weight slowly back down. This is different from isometric contractions, where the muscle generates force without changing length, and the term often isn’t used to describe motions against a changing load. The pairing of concentric and eccentric captures the two ways a muscle can produce force while actively changing length under load.