Ground Reaction Force

Ground reaction force (GRF) - The force exerted by the ground on the body in contact with it. For example, when a runner's foot strikes the ground with a force equal to the mass of the individual times their acceleration due to gravity, momentum and muscular exertion, the ground exerts an equal and opposite force on the runner's foot.

• GRF is often measured in research studies using force plates as a means of quantitatively measuring the force generated by an individual.