"Muscles that work like this are called antagonistic 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."

"antagonist: This type of muscle acts as opposing muscle to agonists, usually contracting as a means of returning the limb to its original resting position.
agonist: These muscles are typically associates with the movement itself, and are sometimes referred to as prime movers. They contract while another muscle relaxes."