Details on Subjects and Experimental Trials used for Regression Fits.

: Body weight (kg), and : Body height (m), and : Minimum and maximum gait speed (m/s) and : Minimum and maximum hip quasi-stiffness in extension stage (Nm/rad) and : Minimum and maximum hip quasi-stiffness in flexion stage (Nm/rad) and : Minimum and maximum hip excursion in extension stage (deg) and : Minimum and maximum hip excursion in flexion stage (deg): Average of the linear fit on moment-angle curve in extension stage: Average of the linear fit on moment-angle curve in flexion stage‡Data collected at Human PoWeR Lab, NC State University [16]†Data collected at Biomechanics Lab, East Carolina University [55]•Data collected at Laboratory of Biomedical Technologies at Politecnico Di Milano.