footoff

Footoff is a term used in biomechanics and robotics to denote the brief transitional moment at the end of the stance phase of the gait cycle when the foot ceases full contact with the ground and begins the toe-off push-off. It describes the moment during which plantar pressure falls below a threshold and the ground reaction forces shift from a supporting role toward propulsion. Footoff is distinct from toe-off, which refers to the actual lift-off of the forefoot, and from heel strike, the initial contact of the foot with the ground.

Origin and usage: The term footoff appears in biomechanical glossaries and conference discussions in the early 2010s. While its exact origin is not universally agreed upon, it is generally used by researchers studying transitional phases of gait and the timing of foot-ground interactions.

Measurement and modeling: Footoff is typically identified in instrumented gait analysis using force plates, motion capture, or plantar pressure sensors. In computational models, footoff serves as a marker for updating the contact state and can improve estimates of energy expenditure and propulsion in simulations of human or robotic locomotion.

Applications and implications: In human biomechanics, footoff informs assessments of walking efficiency, rehabilitation progress, and the design of assistive devices. In robotics, footoff timing helps control strategies for legged robots to enhance stability, energy efficiency, and responsiveness to terrain.

Limitations: Some sources do not treat footoff as a separate phase, instead incorporating it into late stance or toe-off definitions, leading to varying reporting practices across studies.

See also: Toe-off, Heel strike, Gait cycle, Plantar pressure, Ground reaction force, Robotic locomotion.