Muscle Terminology and Major Muscles of the Body
It is important for massage therapists and other bodyworkers dealing with soft tissue to become fa-miliar with terms relating to muscle and muscle contraction.
The most stationary point of muscle attachment, usually the proximal point, is called the origin. The in-sertion is the point of muscle attachment that is moremobile and moves with the bone, usually the more dis-tal point. The changes produced to the joint by the contraction of the muscle are called the action(s) of the muscle. The action of a muscle can be identified by knowledge of its origin and insertion which, in turn, enables health professionals to effectively treat indi-viduals who have difficulty executing certain move- ments. It must be remembered that difficulty moving specific bones is not always a result of malfunction of muscles that produce the movement. Problems in joint architecture, ligament structure, and skin over the joint, among others, may restrict movement.
Depending on the attachment site of a muscle to a bone, the joint can be moved in many directions.
These directions of movement have specific terms, and the standard terms for all movements are ex-plained.
The movements produced by muscles are grouped according to their primary actions. A muscle is con-sidered to be a prime mover, or agonist, if it is the main muscle producing a particular movement. For example, the biceps brachii is the prime mover for flexion of the forearm. Antagonists are prime movers that oppose the action of the agonist. In the above ex-ample, the triceps brachii located in the back of the upper arm is the antagonist.
A muscle that assists a prime mover in performing the movement is called a synergist. Synergists may assist by producing more pull at the insertion point or stabilizing the point of origin of the prime mover. They include muscles that often help the prime mover initiate the action when the power produced by the prime mover is not at its maximum. Fixators are muscles that stabilize the origin of the prime mover to increase efficiency.
One of the most daunting tasks for any health pro-fessional is to learn the names of muscles. But this process is simplified if the meaning of certain terms is understood. Many muscles are named according to organization of the fascicle, location, structure, size, shape, action, origin, insertion, and other striking fea-tures.