Intentional compensation for selective loading affecting human gait phases.

The locomotor strategies used by 12 subjects, instructed to hold their walking speed constant, were examined under various dynamic conditions in order to determine the means by which subjects can act upon their basic locomotor synergy. The dynamic conditions were modified either by adding a load or applying an impeding force. These modifications were designed to selectively affect either the stance phase or the swing phase. The results show that (a) subjects were able to rapidly calibrate their efforts to hold their walking speed constant, (b) in all conditions, the same walking speed was achieved with the same stride lengths and durations, and (c) at the within-cycle level, a change in duration synergically affected both phases and not just the perturbed one. The above results are discussed in terms of intentionally controlled parameters. Because cadence is closely linked to walking speed, it can be used as feedback; the control of walking speed in our experiments may thus be achieved simply by increasing the exerted force until the same cadence is produced.