5-16. THE SKELETOMUSCULAR UNIT
The skeletomuscular unit (Figure 5-3) is a working concept of muscle and
skeleton producing motion. The components of an S-M unit are: bones, a joint, and
Figure 5-3. The skeletomuscular unit.
a. Bones. Bones act as levers and as attachment sites for skeletal muscles.
b. Joint (Articulation). The joint is the center, fulcrum, point, or axis of motion.
c. Skeletal Muscle(s). Skeletal muscles apply the forces for motion. Any given
motion utilizes a group of muscles working together.
5-17. POTENTIAL ROLES OF A SKELETAL MUSCLE
During a given rotary motion, a skeletal muscle may have one of several different
roles to play. During the motion, a muscle may change from one role to another.
a. Prime Mover. Of a group of muscles acting upon a moving part, the one
producing the strongest and most direct force is in the prime mover role. Its force is in
the direction of the motion being produced.