What is the term for the relaxed muscle in a pair that performs opposing actions?

The term for the relaxed muscle in a pair that performs opposing actions is antagonists. When muscles work in pairs, one muscle contracts to produce movement while the other muscle, the antagonist, relaxes to allow that movement to occur. This opposition is critical for controlled movement and balance. For example, when the biceps contract to flex the arm at the elbow, the triceps act as the antagonist by relaxing, which helps to facilitate smooth and coordinated movement.

Understanding the role of antagonistic muscles is essential in biomechanics, as it highlights the importance of muscle balance and the mechanics of movement in the body. Without antagonists, movement would be jerky and uncontrolled, as there would be no muscle to provide resistance and control.