What is cross-bridge cycling?

In the context of muscular contraction, cross-bridge cycling refers to the process by which myosin heads in muscle cells alternately bind to and detach from actin filaments. A cross-bridge is formed when a myosin head attaches to an actin filament. This actin-myosin cross-bridge formation pulls the actin inward, shortening the sarcomere length, which results in a contraction. The energy for the actin-myosin cross-bridge formation is provided by ATP. Immediately after the cross-bridge is formed, the myosin head detaches from the actin filament, breaking the cross-bridge. This repeated attachment and detachment of myosin and actin is known as cross-bridge cycling. It is identified in all muscle types, including skeletal, cardiac, and smooth muscles.