Speeding up: Discrete mediolateral perturbations increased self-paced walking speed in young and older adults

Abstract

BackgroundIn uncertain environments and with increasing age humans often walk slower while taking shorter, quicker, and wider steps, reflective of a cautious gait. Understanding when humans opt to use a cautious gait and the differences in gait strategies used as people age could be examined with perturbations on a self-paced treadmill that allows participants to adjust their walking speed. Adding varying degrees of unpredictability, an inherent element of real-world walking could also improve understanding of when specific gait strategies are used. Research questionWe investigated how healthy young and older adults adjust their gait strategies when responding to perturbations of varying unpredictability. We hypothesized that more unpredictable perturbations would produce more cautious gait strategies and be more pronounced in older adults than young adults. MethodsTen young and ten older adults walked on a self-paced treadmill with discrete mediolateral treadmill shift perturbations. We changed the shift magnitude and/or the timing of the perturbations during the gait cycle to vary perturbation unpredictability. We analyzed walking speed and step kinematics from treadmill and motion capture data. ResultsSurprisingly, participants walked faster not slower for the conditions with perturbations. Even more surprising older adults walked faster overall than young adults. As expected, participants took faster and wider steps for the most unpredictable perturbation but also took longer steps which was not expected. Step kinematic variability and average step width also increased as perturbation unpredictability increased suggesting that the more unpredictable conditions demanded greater balance control. Additionally, older adults had greater step kinematic variability, highlighted further using detrended step length variability, compared to young adults SignificanceOverall, these findings provide new insights about gait strategies and suggest that perturbations such as discrete mediolateral treadmill shifts can potentially be designed to encourage participants to walk faster if it is beneficial.