What is the mechanical force of muscle contraction generated by?

The mechanical force of muscle contraction is generated by the interaction between the thick (myosin) and thin (actin) filaments within the muscle fibers. When a muscle receives a signal from the nervous system, calcium ions are released into the muscle cell. These calcium ions bind to the protein troponin, which allows the myosin heads to bind to the actin filaments. The myosin heads then undergo a series of conformational changes, pulling the actin filaments towards the center of the muscle fiber. This process, known as the cross-bridge cycle, generates the mechanical force of muscle contraction.