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The Journal of Experimental Biology 205, 3413-3422 (2002)
Copyright © 2002 The Company of Biologists Limited

Pendular energy transduction within the step in human walking

G. A. Cavagna^1,*, P. A. Willems², M. A. Legramandi¹ and N. C. Heglund²

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

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

Accepted 12 July 2002

During walking, the centre of mass of the body moves like that of a `square wheel': with each step cycle, some of its kinetic energy, E_k, is converted into gravitational potential energy, E_p, and then back into kinetic energy. To move the centre of mass, the locomotory muscles must supply only the power required to overcome the losses occurring during this energy transduction. African women carry loads of up to 20% of their body weight on the head without increasing their energy expenditure. This occurs as a result of an unexplained, more effective energy transduction between E_k and E_p than that of Europeans. In this study we measured the value of the E_k to E_p transduction at each instant in time during the step in African women and European subjects during level walking at 3.5-5.5 km h^-1, both unloaded and carrying loads spanning 20-30% of their body weight. A simulation of the changes in E_k and E_p during the step by sinusoidal curves was used for comparison. It was found that loading improves the transduction of E_p to E_k during the descent of the centre of mass. The improvement is not significant in European subjects, whereas it is highly significant in African women.

Key words: locomotion, walking, recovery, energy expenditure, human

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