During muscle contraction, how do actin and myosin interact?

During muscle contraction, actin and myosin interact through a process known as the sliding filament mechanism. In this process, the myosin filaments have protrusions known as crossbridges that attach to specific binding sites on the actin filaments. Once attached, the myosin heads pivot, pulling the actin filaments toward the center of the sarcomere. This sliding action causes the muscle to shorten and contract.

This interaction is crucial for muscle function and is facilitated by the presence of calcium ions and ATP, which allow myosin to bind to actin and release during the contraction cycle. The movement does not involve the actin and myosin filaments themselves shortening; rather, they slide past each other, leading to overall muscle contraction. This understanding is fundamental in exercise physiology and biomechanics, as it highlights how muscle contractions generate force and movement.