Fixator: A synergist muscle that works to immobilize a bone or the origin of a muscle. They tend to stabilize the proximal end so that movement can occur at the distal end.
Fixators help provide a firm base for a prime mover to perform its function without unwanted movement of another structure. The muscles that stabilize the scapula are fixators when they prevent movement of the scapula during elbow flexion and other movements, for example. Since the biceps are attached to the scapula on the proximal originating end as well as to the radius, shortening of this muscle would result not only in movement of the radius but also of the scapula, bringing the two closer together.
The scapula fixators prevent this scapula movement so that isolated elbow flexion can occur. Fixators work primarily in an isometric fashion, although some slight movement of a stabilized part or segment may occur as adjustments in body position require it.
Some sources consider fixators to be a separate class from synergists, which creates confusion and gray areas. Most sources, however, consider fixators a specific type of synergist. It is possible for a muscle to act as a fixator in one movement but as an agonist or antagonist in another movement, depending on the specific movement and which point is fixed.
This page created 08 Nov 2011 18:14
Last updated 27 Feb 2016 22:57