Torque

Torque is a rotational force that causes an object to rotate around an axis. Linear force results in torque when applied to a lever that moves in a circle around an axis. In the human body, most muscles produce torque, because most bones move around the fixed axis of a joint. For example, during squats the gluteus maximus contracts (linear force), pulling the femur (lever), around the hip (axis), resulting in extension (a circular motion). Note, although "external rotation" and "internal rotation" includes "rotation" in the name of the action, all joint actions are the result of rotational torque forces.