- The primary role of a fixator muscle is to provide joint stabilization during a movement.
- When a particular muscle contracts to produce movement, other muscles, called fixators, contract simultaneously to stabilize the origin of the prime mover.
- This stabilization is essential because it allows the prime mover to act more effectively and efficiently by providing a firm base, preventing unwanted movement at adjacent joints.

- In contrast, muscles involved in the initiation of contraction (Option 1) are typically called prime movers or agonists, while those opposing the prime mover (Option 3) are called antagonists. Additionally, muscles assist in relaxation through nervous system regulation, but this is not the function of fixators (Option 4).

In summary, the fixator muscle’s main function is to stabilize joints to allow smooth and controlled movement.

Reference: Gray’s Anatomy, 42nd Edition, Muscle Function and Mechanics, Chapter 6, Page 112