LCCW Skeletal Anatomy Practice Test 2026 – Your Comprehensive All-in-One Guide to Exam Success!

An antagonist muscle is the one that lengthens and controls motion, opposing the action of the primary mover. In most movements, the agonist (the prime mover) contracts to shorten and produce the movement, while the antagonist lengthens to slow down or brake the motion and help stabilize the joint. For example, when you bend your elbow, the biceps brachii acts as the agonist and shortens to flex the elbow, while the triceps brachii lengthens to allow the movement to happen smoothly and to control its speed. The muscle that stabilizes joints during motion and the muscle that performs the same joint motions as the agonist fit different roles and don’t describe the antagonist.