Fig. 8. The horizontal ground reaction force is only negative for the first 25% of ground contact, which means that the force vector stays anterior to the knee (the leg) throughout ground contact. Horizontal velocity decreases slightly during the first 25% of contact, which coincides with the negative (braking) horizontal force. For comparison, the mean horizontal force during trotting at 3.25 m s^-1 (which is a speed very similar to mean speed during the jump) is shown. The amount of braking that occurs during trotting is greater (larger area) than during jumping. The braking impulse during trotting is roughly twice that of jumping (0.06 Ns kg^-1 vs 0.03 Ns kg^-1). The curve represents the mean horizontal force for all trials.