The reasoning: ATP‑driven cycling regulated by Ca²⁺
Cycle: (1) ATP binds → myosin detaches; (2) hydrolysis → head cocked (ADP + Pi bound); (3) weak then strong actin binding; (4) Pi release → power stroke; (5) ADP release → rigor (strongly bound) state, awaiting ATP. Ca²⁺ (via troponin) gates access to actin; ATP powers detachment and repriming.