Muscle contraction in its most basic form involves the interaction of the two types of myofilaments: actin and myosin. During this process, known as the sliding filament model of muscle contraction, the sarcomere—the region of overlapping actin and myosin myofilaments—shortens in response to muscle stimulation. The sarcomere repeats itself along the length of skeletal and cardiac muscle fibres.

Each sarcomere is bounded by Z-lines that ultimately move toward each other when the thin actin myofilament moves past the thicker myosin myofilament. The actin myofilament pulls on the ends of the region of contraction. The interaction of myosin and actin myofilaments require ATP. The shortening of the sarcomere and the change in the various zones and bands that make up the sarcomere are what make skeletal muscles striated.