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First published online June 6, 2005
Journal of Experimental Biology 208, 2333-2346 (2005)
Published by The Company of Biologists 2005
doi: 10.1242/jeb.01661

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Effect of an increase in gravity on the power output and the rebound of the body in human running

G. A. Cavagna^1,*, N. C. Heglund² and P. A. Willems²

¹ Istituto di Fisiologia Umana, Università degli Studi di Milano, 20133 Milan, Italy
² Unité de Physiologie et Biomécanique de la Locomotion, Université catholique de Louvain, 1348 Louvain-la-Neuve, Belgium

^* Author for correspondence (e-mail: giovanni.cavagna{at}unimi.it)

Accepted 25 April 2005

The effect of an increase in gravity on the mechanics of running has been studied by using a force platform fixed to the floor of an aircraft undergoing flight profiles, resulting in a simulated gravity of 1.3 g. The power spent to maintain the motion of the centre of mass of the body is 1.3 times greater than on Earth, due to a similar increase of both the power spent against gravity and to sustain the forward speed changes. This indicates that the average vertical displacement per unit distance and the average direction of the push are unchanged. The increase in power is mainly due to an increase in step frequency rather than to an increase in the work done at each step. The increase in step frequency in turn is mainly due to a decreased duration of the effective aerial phase (when the vertical force is less than body weight), rather than an increase in the stiffness of the bouncing system. The maximal speed where step frequency can match the resonant frequency of the bouncing system is increased by 5 km h^–1 at 1.3 g. These results suggest a similar running mechanics at higher gravity, maintained at the expense of greater energy expenditure.

Key words: locomotion, running, gravity, human