Contributions of metabolic and temporal costs to human gait selection

Abstract

<jats:p>Humans naturally select several parameters within a gait that correspond with minimizing metabolic cost. Much less is understood about the role of metabolic cost in selecting between gaits. Here, we asked participants to decide between walking or running out and back to different gait specific markers. The distance of the walking marker was adjusted after each decision to identify relative distances where individuals switched gait preferences. We found that neither minimizing solely metabolic energy nor minimizing solely movement time could predict how the group decided between gaits. Of our twenty participants, six behaved in a way that tended towards minimizing metabolic energy, while eight favoured strategies that tended more towards minimizing movement time. The remaining six participants could not be explained by minimizing a single cost. We provide evidence that humans consider not just a single movement cost, but instead a weighted combination of these conflicting costs with their relative contributions varying across participants. Individuals who placed a higher relative value on time ran faster than individuals who placed a higher relative value on metabolic energy. Sensitivity to temporal costs also explained variability in an individual's preferred velocity as a function of increasing running distance. Interestingly, these differences in velocity both within and across participants were absent in walking, possibly due to a steeper metabolic cost of transport curve. We conclude that metabolic cost plays an essential, but not exclusive role in gait decisions.</jats:p>

Preferred walking speed on rough terrain; is it all about energetics?

“…In summary, based on both the current findings, which show a difference between the speed that minimizes the COT and the preferred speed on rough terrain, and previous research (Brown et al, 2002;Clark-Carter et al, 1986;Monsch et al, 2012;Schniepp et al, 2014), it seems that simply minimizing COT does not fully represent the human objective function for walking speed. Other walking conditions should be examined to investigate additional parameters that might appear in the cost function, such as stability, reward and time-saving (Summerside, et al, 2018). Present study Goldman, 1971 Pandolf et al, 1977 D 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 Metabolic rate (W kg -1 )…”

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

“…Previous work suggests that time 11 , comfort 25 , and stability 13 may also contribute to a person’s gait choices. We held time constant across all choices in our study, so while time and energy may both influence a person’s choice of gait, even these factors combined cannot fully explain step length-width preferences.…”

“…gait speed) to investigate people's choices as a function of movement. Few studies have explicitly measured movement preferences [18][19][20][21] , particularly for walking 11 . Ultimately, the goal of many rehabilitation interventions is to change a person's movement behavior.…”

Increasing step width reduces the requirements for subtalar joint moments and powers

“…This is partly because of their reduced capacity to recycle elastic energy and an increased requirement to activate larger volumes of muscle as these muscles typically have longer fibre lengths (Biewener and Roberts, 2000;Farris and Sawicki, 2012;Roberts et al, 1997). Metabolic cost plays an essential role in the movement strategy employed by humans, however, it's contribution is not exclusive (Summerside et al, 2018). Gait movement is a weighted decision of several parameters based on the individual including stability, safety and/or perceived comfort, parameters (Daley, 2008;Daley and Usherwood, 2010;Grimmer et al, 2008).…”