Final answer:
The power stroke of myosin is preceded by the formation of a cross-bridge between myosin and actin, whereby the myosin head with ADP and Pi attaches to actin, leading to muscle contraction.
Step-by-step explanation:
The power stroke of myosin in the cross-bridge cycle is immediately preceded by the formation of a cross-bridge between the myosin head and actin. This event occurs when the myosin head, which has adenosine diphosphate (ADP) and inorganic phosphate (Pi) bound to it, attaches to an actin filament. As myosin releases the Pi, it forms a stronger attachment to actin, and the myosin head then moves, pulling the actin filament toward the M-line in a process referred to as the power stroke. The sarcomere shortens and muscle contraction occurs. Following this, ADP is released and another molecule of ATP binds to the myosin head, causing it to detach from actin and allowing the cycle to repeat.