According to the Sliding-Filament Theory, what happens during muscle contraction?

In the context of the Sliding-Filament Theory, the correct understanding is that during muscle contraction, thin actin filaments slide over thick myosin filaments. This process is fundamental to how muscles generate force and produce movement. When a muscle receives a signal for contraction, myosin heads engage with binding sites on the actin filaments, forming cross-bridges. As the myosin heads pull the actin filaments toward the center of the sarcomere, this sliding action causes the entire muscle fiber to contract and shorten.

This theory has been extensively studied and is widely accepted in muscle physiology. It demonstrates that muscle contraction does not result from the shortening of the filaments themselves, but rather from the sliding motion between them. This key detail helps clarify that the muscle fibers' contraction is achieved through this interaction rather than through the contraction or shortening of the filaments themselves, highlighting the intricate interplay between these structures during physical activity.