The sliding filament theory of muscular contraction states ______.

The sliding filament theory of muscular contraction describes the process by which muscles contract at the microscopic level. According to this theory, the key action that produces muscle contraction involves the thin actin filaments sliding over the thick myosin filaments. This interaction is facilitated by the formation of cross-bridges between the myosin heads and the binding sites on the actin filaments.

When a muscle is stimulated to contract, the myosin heads extend and attach to the actin filaments, pulling them inward as they pivot and release. This sliding mechanism shortens the distance between the Z-lines of the muscle fiber, ultimately leading to muscle contraction.

This process is crucial for generating force and movement in skeletal muscles. Therefore, the statement that thin actin filaments move over thick myosin filaments captures the fundamental mechanism of how muscles produce contraction and generate force. The other options do not accurately describe the sliding filament theory or its role in muscular contraction.