contraction steps: 10.) Myosin ATPase, an enzyme in the head, hydrolyzes this ATP to ADP + P. This activates the head, which "cocks" into an extended, high-energy position. The head keeps the ADP and phosphate group bound to it. 11.) The cocked myosin binds to an exposed active site on the thin filament, forming a cross-bridge between the myosin and actin. 12.) Myosin releases the ADP and phosphate and flexes into a bent, low-energy position, tugging the thin filament along with it. This is called the power stroke. The head remains bound to actin until it binds a new ATP 13.) Upon binding more ATP, myosin releases the actin. Process is repeated- it will hydrolyze ATP, recock (the recovery stroke), attach to a new active site farther down the thin filament, and produce another power stroke.