Bilateral temporal control determines mediolateral margins of stability in symmetric and asymmetric human walking

Tom J W Buurke,Claudine J C Lamoth,Lucas H V Van Der Woude,Rob Den Otter,At L Hof

doi:10.1038/s41598-019-49033-z

Tom J W Buurke, Claudine J C Lamoth + Show 3 more

Open Access

https://doi.org/10.1038/s41598-019-49033-z

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Abstract

Human bipedal gait requires active control of mediolateral dynamic balance to stay upright. The margin of stability is considered a measure of dynamic balance, and larger margins are by many authors assumed to reflect better balance control. The inverted pendulum model of gait indicates that changes in the mediolateral margin of stability are related to changes in bilateral single support times. We propose updated equations for the mediolateral margin of stability in temporally symmetric and asymmetric gait, which now include the single support times of both legs. Based on these equations, we study the relation between bilateral single support times and the mediolateral margin of stability in symmetric, asymmetric, and adaptive human gait. In all conditions, the mediolateral margin of stability during walking followed predictably from bilateral single support times, whereas foot placement co-varied less with the mediolateral margin of stability. Overall, these results demonstrate that the bilateral temporal regulation of gait profoundly affects the mediolateral margin of stability. By exploiting the passive dynamics of bipedal gait, bilateral temporal control may be an efficient mechanism to safeguard dynamic stability during walking, and keep an inherently unstable moving human body upright.

Highlights

IntroductionBipedal gait (as seen in humans) is more energy efficient than quadrupedal gait (as seen in most other mammals)[1], but to stay upright it requires active control of mediolateral dynamic balance[2,3]
Bipedal gait is more energy efficient than quadrupedal gait[1], but to stay upright it requires active control of mediolateral dynamic balance[2,3]
In Experiment A we assessed whether single support time and mediolateral margin of stability are related in symmetric walking

Summary

Introduction

Bipedal gait (as seen in humans) is more energy efficient than quadrupedal gait (as seen in most other mammals)[1], but to stay upright it requires active control of mediolateral dynamic balance[2,3]. When single support time decreases, the inverted pendulum, and the centre of mass, has less time to fall to the side before foot placement. In other words, this reduces the lateral sway of the centre of mass. When single support time decreases, the extrapolated centre of mass excursion is smaller, the distance between extrapolated centre of mass and base of support increases, resulting in a larger mediolateral margin of stability. The inverted pendulum model indicates that the relation between single support time and the mediolateral margin of stability will change once gait becomes asymmetric. Previously[7], the relation for mediolateral margin of stability b has been described as in Eq 1: b

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