We studied the isolated and combined energy costs of walking with asymmetry in step times and step lengths. We instructed healthy participants to walk with prescribed levels of asymmetry in only step times, only step lengths and with concurrent asymmetry.
We found that the rate of energy use is ~2.5 greater with step time asymmetry than step length asymmetry.
Cost of taking 2 steps of unequal length predicted cost of length asymmetry. Supporting prev. work from @RodgerKram, cost of time asymmetry exceeded cost predicted from taking 2 steps of unequal time. Our interpretation: only time asymmetry is a ‘true’ asymmetry cost.
Cost of walking with concurrent asymmetry in step times and step lengths was best explained by the cost of step time asymmetry alone; this suggests that costs of time and length asymmetry do not interact and supports time asymmetry as ‘true’ cost of asymmetry.
Last, we found that much of the increased metabolic cost of asymmetry was explained by positive mechanical power produced during single support phases to compensate for a net loss of center of mass power incurred during double support phases.
Many thanks to Julia Choi and committee members @BrianUmberger, @locomocn and Richard van Emmerik. And a special thanks to @jamesmfinley for organizing the symposium at @AmSocBiomech in 2017 that inspired many of the questions pursued in the dissertation.
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