The fixator muscles stabilize a section of the body when another section moves. The muscle allows the antagonist muscles to move effectively during normal movement or exercise.
Some muscles attach to one or more bones. When a person performs a bicep curl, for example, the bicep flexes the elbow. The bicep connects to the bone in two places, and the fixator allows one area to move during the curl. As the bicep contracts, the radius and scapula come together. The fixator muscle prevents the scapula from moving in order to achieve full movement of the radius area. Most fixator muscles surround the hip and shoulder bones.