Structure & Function of Muscle | CSCS Chapter 1

Muscle physiology provides the foundational understanding necessary for effective training, periodization, and programming. Skeletal muscle functions as an organ where connective tissue layers—the epimysium, perimysium, and endomysium—transmit tension from the point of origin to the insertion. At the cellular level, the motor unit serves as the functional contractile unit, consisting of an alpha motor neuron and its innervated fibers. The sliding filament theory explains muscle contraction through the interaction of actin and myosin filaments within the sarcomere. Driven by an action potential, calcium release from the sarcoplasmic reticulum enables these filaments to bind. In the presence of ATP, myosin heads perform power strokes that shorten the sarcomere, generating force. Optimal force production depends on the number of cross-bridges formed, highlighting the direct relationship between muscle size, fiber length, and mechanical output.