Mechanical work performed by the human model on the individual belts vs. step length asymmetry for minimum effort gait solutions for 1:1 through 3:1 belt speed ratios, separated into individual components: Rate of positive work (A), negative work (B), and net work (C) performed by the fast belt on the corresponding leg; Rate of positive work (D), negative work (E), and net work (F) net work performed by the slow belt on the correspondsing leg.