APPLIED RADIOLOGICAL ANATOMY

Detailed explanation-1: -Muscles that work like this are called antagonist ic pairs. In an antagonistic muscle pair as one muscle contracts the other muscle relaxes or lengthens. The muscle that is contracting is called the agonist and the muscle that is relaxing or lengthening is called the antagonist.

Detailed explanation-2: -An antagonist muscle is one which has an action directly opposite that of the agonist. When an agonist undergoes a concentric contraction, the antagonist undergoes an eccentric contraction to guide the movement and to stabilize the joint.