What term describes a muscle that works in cooperation with another muscle?

The term that describes a muscle working in cooperation with another muscle is "synergist." Synergist muscles assist the agonist muscles (the primary movers) during an action to enhance the effectiveness of a movement. For example, during a bicep curl, the biceps brachii acts as the agonist, while muscles such as the brachialis and brachioradialis function as synergists to help stabilize and support the movement of the elbow joint.

Understanding the role of synergists is crucial in biomechanics and strength training, as they contribute to the coordination and balance necessary for smooth and efficient movement. By recognizing which muscles act as synergists, individuals can better design effective workout routines and rehabilitation programs that consider muscle cooperation and balance during physical activities.