Antagonist Muscle

The antagonist muscle is the muscle that opposes the action of the primary mover in a given movement.

An antagonist muscle can be the agonist muscle, too; it depends on which motion is the focus. The antagonist muscles of bending your elbow are the triceps brachii while the agonists are the biceps brachii!

A child in a red dress bends their elbow to carry a basket of flowers. A label for the antagonist muscle points to the back of the upper arm, and a label for the agonist muscle points to the front of the upper arm.