Basic definitions of Interactions of Skeletal Muscles in the Body (e.g., agonist, synergist)

Agonist

The main muscle responsible for generating a specific movement during an action.

Synergist

A muscle that assists the agonist in performing a movement. It can also be a fixator that stabilizes the bone that is the attachment for the prime mover’s origin.

Antagonist

Muscles with the opposite action of the agonist, they work in maintaining posture and rapid actions.

Origin

the end of the muscle attached to the fixed bone (bone that doesn’t move during contraction)

Insertion

bone that moves toward the origin

flexion

Bending a joint to decrease the angle.

Extention

Increase the angle between 2 structures