Pushoff

Pushoff, often written push-off, is the action of propelling the body away from a fixed object by exerting a force against it. The contact force on the surface and the equal and opposite reaction on the mover produce an impulse that changes the mover’s momentum, enabling motion. The direction, magnitude, and duration of the push determine the resulting velocity and trajectory.

Pushoff occurs in a wide range of activities. It is used to initiate movement from rest, to alter direction, or to gain distance in sports such as jumping, skating, diving, and gymnastics. In locomotion, the term is commonly applied to the push-off phase of gait, when the foot plantarflexes against the ground to propel the body forward.

Mechanics and measurement are governed by Newton’s laws. The impulse delivered during a pushoff equals the integral of the contact force over time (J = ∫F dt), and the work done relates to the displacement of the point of contact (W = ∫F ds). Ground reaction forces can be measured with force plates, and pushoff dynamics are analyzed using biomechanical models that consider muscle activity, joint angles, and surface properties. The efficiency of a pushoff depends on appropriate timing, force direction, and surface compliance; excessive or poorly directed forces can increase injury risk.

In addition to athletics and biomechanics, pushoff concepts are used in robotics, virtual reality, and haptic interfaces, where controlled push-off interactions enable movement, exploration, or task manipulation. Etymologically, it derives from the verb push off, referring to detaching from a surface to move.