Muscle chiefly or primarily responsible for any given motion
Opposite of the agonist
While not the Prime mover for a given motion, a synergist is capable of helping the prime mover. Any muscle that assist the agonist in producing the main action
A muscle contracts to hold a body part immobile, while another part is moving. In most cases proximal joints are stabilized by muscle contractions during movement of more distal joints
Examples of Stabilizer
Quads hold knee in extension whiel standing on tip toes.
Quads holding leg while fine tune the gas pedal
Gracilis, sartorius and gastrocnemius act as synergists for flexion of the knee.
During pronation of the forearm, the assisting muscles will be the pronator quadratus and brachioradialis
Example of an Agonist
Upper Trapezius is the agonist for elevation of the scapula since it initiates the motion.
Hamstrings serve as agonists for flexion of the knee.
Pronator Teres is the prime mover for pronation of the forearm
Often doesn’t function near the main action but supports another part of the body in position while the main action occurs