Probability of Lateral Instability While Walking on Winding Paths

Abstract

ABSTRACTPeople with balance impairments often struggle performing turns or lateral maneuvers, which can increase risk of falls and injuries. Here we asked how people maintain mediolateral balance when walking on non-straight winding paths. Twenty-four healthy adults (12F/12M; 25.8±3.5 yrs) participated. Each walked on each of six paths projected onto a treadmill, comprised of three pseudo-random path oscillation frequency combinations (straight, slowly-winding, quickly-winding), each presented at either wide or narrow width. We quantified stepping errors as the percent of steps taken off each path. We quantified minimum mediolateral Margin of Stability (MoSL) at each step and calculated means (μ) and standard deviations (σ) for each trial. We calculated lateral Probability of Instability (PoIL) as participants’ statistical risk of taking unstable (MoSL< 0) steps. Onnarrowerpaths, participants made more stepping errors on the winding paths (p < 0.001) and walked with smallerμ(MoSL) on all paths (p < 0.001), but exhibited significantly increasedPoILonly on the slowly-winding path (p < 0.001). Onwindypaths, participants made increasingly more stepping errors (p < 0.001) for increasingly windier narrow paths (p < 0.001). They consistently walked with smallerμ(MoSL), largerσ(MoSL), and increasedPoILon increasingly windier paths of both widths (all p < 0.001). Though many took numerous unstable steps, no participantfell. Our results demonstrate healthy adults’ ability both to trade off increased risk of lateral instability for greater maneuverability, and to employ highly-versatile stepping strategies to still maintain balance while walking.