Details on Subjects and Experimental Trials used for Regression Fits.

<p>: Body weight (kg), and : Body height (m),</p><p> and : Minimum and maximum gait speed (m/s).</p><p> and : Minimum and maximum quasi-stiffness in flexion stage (Nm/rad).</p><p> and : Minimum and maximum quasi-stiffness in extension stage (Nm/rad).</p><p> and : Minimum quasi-stiffness in weight-acceptance phase (Nm/rad).</p><p> and : Minimum and maximum knee excursion in weight-acceptance phase (deg).</p><p>: Average of the linear fit on moment-angle curve in flexion stage.</p><p>: Average of the linear fit on moment-angle curve in extension stage.</p><p>: Froude number.</p>‡<p>: Data collected at Human PoWeR Lab, NC State University <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0059993#pone.0059993-Farris1" target="_blank">[24]</a>.</p>†<p>: Data collected at Biomechanics Lab, East Carolina University <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0059993#pone.0059993-Hortobgyi1" target="_blank">[29]</a>.