Figure 1. Example ground reaction force-time history and the five discrete dependent variables. F1 = first peak ground reaction force; F2 = second peak ground reaction force; F1LR = average loading rate from the instant of ground contact to the instant of F1; F2LR = average loading rate from the instant of the minimum force between F1 and F2 to the instant of F2. IMP = impulse (total force) calculated from 0-100 ms following initial ground contact.