Is the trapezius a fixator or synergists?

The trapezius muscle can act as both a fixator and a synergist, depending on the specific movement being performed.

As a fixator, the trapezius helps to stabilize the scapula during arm movements. For example, when you raise your arm overhead, the trapezius contracts to help keep the scapula from moving away from the spine.

As a synergist, the trapezius works together with other muscles to produce a specific movement. For example, when you shrug your shoulders, the trapezius contracts along with the levator scapulae muscle to elevate the scapula.

The trapezius muscle is innervated by the accessory nerve (cranial nerve XI).