 Dear students, in this topic, we shall discuss the production of force required for sliding of filaments. The cross bridges between myosin head and actin pull the thin filaments towards the center of sarcomere. The force for this pulling is produced because of partial rotation of the myosin head. Dear students, the rotation of myosin head is produced because the myosin head has four binding sides M1, M2, M3 and M4. These sides sequentially bind with the binding sides present on the actin filament. So, myosin head has four binding sides and actin filament also has binding sides. The binding sides of myosin head are sequentially bind with the binding sides of actin. As the myosin head rotates against the actin filaments, the link is stretched elastically. When myosin head moves, as a result, the link of myosin is stretched elastically. As a result, tension is developed in it. This tension produced in the link is transmitted to the thick myosin filament. This tension provides the force to pull the actin filaments and shorten the sarcomere. Dear students, when rotation of the head is complete, then it dissociates from the actin filament and rotates back to its relaxed position. This dissociation occurs when magnesium ions and ATP bind to the head. In this condition, ATP is hydrolyzed or myosin head also changes its conformation. After some time, the head binds again on the next side of the actin filament. This attachment, rotation and detachment of myosin head is repeated again and again in a cyclic manner. As a result, filaments slide past, this happens in small steps. As a result, sarcomere contraction occurs.