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Daytona Beach


Engineering Fundamentals

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On a treadmill, humans switch from walking to running beyond a characteristic transition speed. Here, we study human choice between walking and running in a more ecological (non-treadmill) setting. We asked subjects to travel a given distance overground in a given allowed time duration. During this task, the subjects carried, and could look at, a stop-watch that counted down to zero. As expected, if the total time available were large, humans walk the whole distance. If the time available were small, humans mostly run. For an intermediate total time, humans often use a mixture of walking at a slow speed and running at a higher speed. With analytical and computational optimization, we show that using a walk-run mixture at intermediate speeds and a walk-rest mixture at the lowest average speeds is predicted by metabolic energy minimization, even with costs for transients { a consequence of non-convex energy curves. Thus, sometimes, steady locomotion may not be energy optimal, and not preferred, even in the absence of fatigue. Assuming similar non-convex energy curves, we conjecture that similar walk-run mixtures may be energetically beneficial to children following a parent and animals on long leashes. Humans and other animals might also benefit energetically from alternating between moving forward and standing still on a slow and sufficiently long treadmill.

Publication Title

Journal of the Royal Society Interface


Royal Society Publishing

Additional Information

Dr. Long was not affiliated with Embry-Riddle Aeronautical University at the time this paper was published.

Required Publisher’s Statement

Long, L. L., III & Srinivasan, M. (2013). Walking, running, and resting under time, distance, and average speed constraints: Optimality of walk-run-rest mixtures. Journal of the Royal Society Interface. 10(81). 20120980. doi:10.1098/rsif.2012.0980