The energy that is released by the hydrolysis of atp by actin is used for:

The energy released is used for assembly of actin filament with myosin head. when myosin is attached to ATP its heads cannot bind to actin and therefore muscle will remain in relaxed form. However during muscle contraction an enzyme referred to as ATPase hydrolyses ATP to ADP and organic phosphate in the process releasing energy. The energy released changes the position of head of myosin which facilatate its binding with actin. Myosin moves towards m-line dragging actin along with it reducing the length of sarcomere leading to muscle contraction.  

C. the forward motion from the car is keeping them in motion