What is the role of a synergist?

• A. Muscle that does most of the work
• B. Muscle that helps the prime mover in a movement
• C. Muscle that opposes or reverses a prime mover
• D. Muscle that stabilizes joints

Answer: (B)

A synergist is a muscle that helps the prime mover perform a movement. It contributes extra force and often stabilizes the joint so the movement is smooth and directed, rather than wobbly or misaligned. For example, in elbow flexion the biceps brachii acts as the prime mover, while synergists like the brachialis and brachioradialis assist by aiding the flexion and keeping the forearm and elbow stable. Some synergists also serve as fixators, holding one end of a muscle steady so the moving end can work more efficiently. This role is different from the muscle that does most of the work (the prime mover) and from the muscle that opposes the movement (the antagonist).