The movement that decreases the angle between joints

(also, prime mover) muscle whose contraction is responsible for producing a particular motion.Although a number of muscles may be involved in an action, the principal muscle involved is called the prime mover, or agonist/p>

(also, prime mover) muscle whose contraction is responsible for producing a particular motion.During forearm flexion (bending the elbow), such as lifting a cup, a muscle called the biceps brachii is actually the prime mover; however, because it can be assisted by the brachialis, the brachialis is called a synergist in this action.Also involved is the brachioradialis which assists the brachialis, and is also considered a synergist.

Synergist that assists an agonist by preventing or reducing movement at another joint, thereby stabilizing the origin of the agonist.

A synergist can also be a fixator that stabilizes the bone that is the attachment for the prime mover’s origin.

muscle that opposes the action of an agonist.A muscle with the opposite action of the prime mover is called an antagonist. Antagonists play two important roles in muscle function: (1) they maintain body or limb position, such as holding the arm out or standing erect; and (2) they control rapid movement, as in shadow boxing without landing a punch or the ability to check the motion of a limb.