What is 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 in a movement. It supports the main action by adding force or refining the motion, and it can stabilize the joint so the primary action proceeds smoothly. For example, in elbow flexion, the biceps brachii is the prime mover, while the brachialis and brachioradialis act as synergists to assist the flexion. They may also limit unwanted movement to keep the motion clean. This is different from the antagonist, which resists or reverses the movement (like the triceps during elbow flexion). Stabilizers or fixators hold a segment steady, but the core idea of a synergist is that it aids the prime mover in producing the movement.