40-50% of body weight is made up of skeletal muscle. Study of skeletal muscle is termed myology. Each of the over 600 skeletal muscles can be thought of as a separate organ.

Skeletal muscle generally work together in coordinated groups. They tend to function in pairs. Or in sets of three, four, or more muscles.

There are over 215 functional pairs of skeletal muscles. Muscles vary significantly in size and shape. Their individual fibers are arranged differently and attach in differing ways to the bones they move.

They all have the same function and behave in the same way……they shorten. As skeletal muscle fibers shorten, their ends are pulled toward the center and contractile force, or tension, is developed in that muscle. The result is movement.

Muscles and Bony Levers Knowledge of lever systems and the points of muscle attachment to bones gives the AT a basis for understanding: Body movement Muscle strength ROM. Maximal muscle strength and maximal ROM at the same joint are mutually exclusive.

The relationship between strength of muscle contraction and range of motion at a given joint is a basic principle of leverage. As a general rule of thumb, if two muscles of equal length cross and act on the same joint. The muscle that inserts (attaches) farther from the joint will produce the more powerful contraction. The muscle inserting closer to the joint will produce the greater range of movement.

Optimum angle of pull Right angle to the long axis of the bone.

Anatomy of Skeletal Muscles Skeletal muscle fibers Connective tissue Nervous tissue Vascular tissue components. Vary considerably in size and shape.

Belly, or gaster. Two tendinous extremities – insertion and origin. Origin is the end that remains fixed or stationary during contraction. Insertion moves when the muscle contracts.

It is distal to the joint and moves toward the origin when the muscle contracts.

Connective Tissue Components Most muscular injury in athletics occur in the connective tissue elements of the muscle. The contraction of muscle cannot occur without these components.

Endomysium – surrounds each muscle fiber. Fascicle – 15 to 40 fibers that are bound into bundles. Perimysium – covers the fascicle and is coarser and more fibrous. Epimysium – thicker outer connective tissue sheath which covers the entire muscle.

Tendon – a strong, tough cord that connects muscle to bone. Aponeurosis – attaches muscle to adjacent structures, usually another muscle. Tendon sheaths – tubular structures of fibrous connective tissue. Enclose certain tendons and have a lining of synovial tissue.