Energy expenditure does not explain step length-width choices during walking

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 experienced two 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. 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.
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