Energy expenditure does not solely explain step length–width choices during walking

Abstract

Healthy young adults have a most preferred walking speed, step length, and step width that are close to energetically optimal. However, people can choose to walk with a multitude of different step lengths and widths, which can vary in both energy expenditure and preference. Here, we further investigate step length-width preferences and their relationship to energy expenditure. In line with a growing body of research, we hypothesized that people's preferred stepping patterns would not be fully explained by metabolic energy expenditure. To test this hypothesis, we used a two-alternative forced-choice paradigm. Fifteen participants walked on an oversized treadmill. Each trial, participants performed two prescribed stepping patterns and then chose the pattern they preferred. Over time, we adapted the choices such that there was 50% chance of choosing one pattern over another (equally preferred). If people's preferences are based solely on metabolic energy expenditure, then these equally preferred stepping patterns should have equal energy expenditure. In contrast, we found that energy expenditure differed across equally preferred step length-width patterns (p<0.001). On average, longer steps with higher energy expenditures were preferred over shorter and wider steps with lower energy expenditures (p<0.001). We also asked participants to rank a set of shorter, wider, and longer steps from most preferred to least preferred, and from most energy expended to least energy expended. Only 7/15 participants had the same rankings for their preferences and perceived energy expenditure. Our results suggest that energy expenditure is not the only factor influencing a person's conscious gait choices.

Assessment and mechanisms of gait robustness and energy efficiency in walking: from models to humans

“…For instance, Hobbelen & Wisse (2008a) showed in a flat-feet walker model that increasing the feedback gain of the ankle push-off torque (assuming no time delay) based on the leading leg's angle can improve gait robustness, but reduces energy efficiency when using a constant hip joint actuation. Arguably, in human walking, the locomotor system aims for a desired balance between multiple costs rather than only energy optimization (Antos et al, 2022;Yandell & Zelik, 2016). Accordingly, my third and last open question reads: Given the selection (solution) of human gait, what are the goal-dependent costs of the locomotor system or why is this gait selected by humans?…”