Final answer:
The formation of a cross-bridge between the myosin head and actin filament, with the myosin head in a cocked position, precedes the power stroke in muscle contraction.
Step-by-step explanation:
The step that automatically precedes the power stroke in muscle contraction is the formation of a cross-bridge between the myosin head and the actin filament.
When the myosin head is cocked, it is in a high-energy configuration and is ready to engage in the power stroke.
The actual power stroke occurs when the myosin head bends, releasing ADP and inorganic phosphate, and pulling the actin filament towards the center of the sarcomere (the M line).
This movement is powered by the stored energy in the myosin head, resulting from ATP hydrolysis.
After the power stroke, the myosin head is in a low-energy position, and a new molecule of ATP must bind to the myosin head, causing the cross-bridge to detach and allowing the cycle to repeat for further muscle contraction.