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

Background: In 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 usedResearch question: We 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 Methods: Ten 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 dataResults: Surprisingly, 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 kine -matic, 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 Significance: Overall, 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.