The myosin head moves toward the M-line, pulling the actin along with it. As the actin is pulled, the filaments move approximately 10 nm toward the M-line. This movement is called the power stroke, as it is the step at which force is produced. During the power stroke, a torque is applied to the crankshaft resulting from the force acting on the piston due to combustion chamber pressure acting through a lever arm, which is proportional to the crank throw R and which varies with crankshaft angular position (θe).
