A critical requirement of stable gait is that individuals can adapt gait to place (target) the feet in a stable position relative to obstructions. The major purpose of this study was to investigate differences in gait control of young (low fall risk) and elderly (high fall risk) individuals when foot placement was constrained to restricted target areas.
Twelve healthy unimpaired young (n = 12, 22.6 ± 2.1 years) and elderly individuals (n = 12, 72.8 ± 5.7 years) walked "at a comfortable speed" across two force-sensitive metal plates embedded in the floor (force platforms). Subjects walked under four conditions; unconstrained, with a target marked on either the first or second platform or with a target on both platforms. Targets were set at widths of 3 cm, 5 cm and 7 cm greater than the subject’s foot length.
The elderly individuals walked significantly slower than the young individuals when walking unconstrained, however when expressed as a ratio of unconstrained gait, in all foot-constrained trials elderly individuals reduced walking speed significantly more than the young controls further accentuating age differences. There was no age-group effect on stance duration when walking unconstrained but large differences were demonstrated in all foot-targeted conditions emphasising the effectiveness of the foot-targeting task for accentuating age-related effects. Despite these adaptations the elderly individuals still had a greater error rate than the young individuals when the target width was only 3 cm greater than foot length.
The kinetic (force) data showed increased support foot braking impulses by the elderly individuals when a target was present on the second platform. Thus, increased risk of slipping in the elderly may be associated with the non-constrained foot when the targeted foot is constrained in its accuracy demands by obstacles. In summary, the foot-targeting task appeared to be more "challenging" to the elderly individuals and significantly accentuated age-related differences in gait control.