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First published online December 1, 2006
Journal of Experimental Biology 209, 4895-4900 (2006)
Published by The Company of Biologists 2006
doi: 10.1242/jeb.02584
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Mechanical energy fluctuations during hill walking: the effects of slope on inverted pendulum exchange

Jinger S. Gottschall* and Rodger Kram

Department of Integrative Physiology, University of Colorado, Boulder, CO 80309, USA

* Author for correspondence at present address: Emory University School of Medicine, Whitehead Research Building, Department of Physiology, 615 Michael Street, Atlanta, GA 30322, USA (e-mail: jgottsc{at}emory.edu)

Accepted 5 October 2006

Humans and other animals exchange gravitational potential energy (GPE) and kinetic energy (KE) of the center of mass during level walking. How effective is this energy exchange during downhill and uphill walking? Based on previous reports and our own reasoning, we expected that during downhill walking, the possibility for mechanical energy exchange would be enhanced and during uphill walking, the possibility for exchange would be reduced. We measured the fluctuations of the mechanical energies for five men and five women walking at 1.25 m s-1. Subjects walked on the level, downhill, and uphill on a force measuring treadmill mounted at 3°, 6° and 9°. We evaluated energy exchange during the single support period based on the GPE and KE fluctuation factors of phase relationship, relative magnitude and extent of symmetry. As expected, during level walking, the GPE and KE curves were out of phase, of similar magnitude, and nearly mirror images so that the fluctuations in combined (GPE+KE) energy were attenuated. During downhill walking, the fluctuations in the combined energy of the center of mass were smaller than those on the level, i.e. mechanical energy exchange was more effective. During uphill walking, the fluctuations in the combined energy of the center of mass were larger than those on the level, i.e. mechanical energy exchange was less effective. Mechanical energy exchange occurred during downhill, level and uphill walking, but it was most effective during downhill walking.

Key words: biomechanics, locomotion, center of mass






© The Company of Biologists Ltd 2006