Abstract
This study investigated the effects of environment complexity and aging on adaptive locomotion under voluntary sampled vision. Eight young and eight old adults, independent walkers with normal or corrected-to-normal vision, volunteered to participate. They walked at a self-selected pace and pointed with the dominant foot at the center of a target flush to the ground followed by the post targeting task (PTT): walking or stair climbing. Intermittent vision was sampled as needed during approach via a hand-held momentary switch connected to a pair of Plato LCD goggles (Translucent Technology, Toronto, ON). A six-camera Visualeyez motion analysis system (PTI, Burnaby, BC) captured kinematic data. The approach footfall variability revealed a two-phase approach with adjustments spread out over the last three steps regardless of experimental manipulations. Older adults decreased the approach velocity as the PTT complexity increased and had, overall, more accurate target pointing as compared to young adults. Intermittent vision resulted in longer cumulative distance over the three adaptive steps and larger cumulative distance variability for the complex PTT only. Intermittent vision condition resulted in longer last step length and swing duration as well as increased last step length and last step stance duration variability. Vision was necessary only for 42% of the approach. Visual samples coincided with the last two steps; the common sampling strategy had one or two samples.
