How is ATP used in myofibril contraction?

ATP is bound to the myosin head to cause detachment of the head from the actin filament, the ATP is then hydrolysed and as a result the myosin head reattaches to the actin filament. The now hydrolysed ATP, in the from of ADP and an inorganic phosphate molecule, is then released causing the myosin head to undergo the power stroke.