Fig. 6. Loaded walking. (A) Average curves of the instantaneous recovery of mechanical energy r(t) for the African women (thick continuous line, mean of 32 steps by four subjects), the European women (thin continuous line, mean of 14 steps by five subjects) and all European subjects (males and females, dotted line, mean of 32 steps by ten subjects). A comparison with Fig. 4 shows that, in all subjects, loading decreases t_pk- and increases r(t) at the beginning of the descent of the centre of mass (t_tr,down), but that this results in a net increase in R_int in the African women only (final value attained by the thick line at the end of the step in B). The corresponding mean values of the parameters for all European subjects and the African women are given in Table 1 (loaded). For further details, see legend to Fig. 4.