Vertical ground reaction force–time waveforms for RFS trials. Vertical ground reaction force–time waveforms for RFS trials. Trials for an individual subject took place at 3.0 m s−1 (A,B), 6.0 m s−1 (C,D) and 8.0 m s−1 (E,F). A, C and E illustrate the model-predicted waveform (solid blue line) from the average kinematics measured during the trial compared with a measured average of the vertical ground reaction force waveforms (solid black line). B, D and F illustrate the sum of the first impulse (dotted red line) and second impulse (dashed green line) to form the total model-predicted waveform (solid blue line). Kenneth P. Clark et al. J Exp Biol 2017;220:247-258 © 2017. Published by The Company of Biologists Ltd