Muscles work in antagonistic pairs when one muscle pulls, the other muscle relaxes.
Explanation:
Antagonistic pair of muscles works by opposing each other's action. This happens because the skeletal muscles that control the movement of bones move unidirectional and can contract or pull in that direction only.
Skeletal muscle movement takes place with contraction of one muscle and relaxation of another muscle. Straightening and bending movements are antagonist type of movements and are provided by the flexor and extensor muscles which antagonize their actions.
During an elbow bending movement of the biceps-triceps muscle pair, the biceps contracts and acts as the agonist and the triceps relaxes or flexes and acts as the antagonist.
