Update and extension of the ‘equivalent slope’ of speed-changing level locomotion in humans: a computational model for shuttle running

Controlled experimental protocols for metabolic cost assessment of speed changing locomotion are quite complex to be designed and managed. The use of the ‘equivalent slope’, i.e. the gradient locomotion at constant speed metabolically equivalent to a level progression in acceleration, proved to be useful to estimate the metabolic cost of speed changing gaits. However, its use with steep slopes forces to extrapolate the experimental cost vs. gradient function for constant running speed, resulting in less reliable estimates. The present study extended the model to work also with deceleration, and revised that predictive equation to be applied to much higher levels of speed change. The case of shuttle running at different distances (from 5+5 to 20+20m) was then investigated throughout the novel approach and software, and the predictions in terms of metabolic cost and efficiency well compare to the experimental data.