Fig. 5. Net mechanical efficiency computed two different ways for walking with the preferred stride rate (0), and with stride rates above (+) and below (–) the preferred rate. Efficiency was computed either including (closed circles) or excluding (open squares) the magnitude of the negative power in the denominator of the efficiency expression (see text for details). When negative power was ignored, the computed efficiency was higher, with the effect being greater at higher stride rates. The overall dependence of mechanical efficiency on stride rate was similar for both expressions.