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Mechanical Work and Metabolic Cost of Walking after Weight Loss in Obese Adolescents


Medicine & Science in Sports & Exercise: October 2010 - Volume 42 - Issue 10 - p 1914-1922
doi: 10.1249/MSS.0b013e3181da8d1e
Applied Sciences

Purpose: This study was performed to investigate whether changes in biomechanical parameters of walking explain the reduction in net metabolic cost after weight loss in obese adolescents.

Methods: Body composition and metabolic and mechanical energy costs of walking at 1.25 m·s−1 were assessed in 16 obese adolescents before and after a weight loss. Center of mass (COM) and foot accelerations were measured using two inertial sensors and integrated twice to determine COM and foot velocities and displacements. Potential and kinetic energy fluctuations of the COM and the external mechanical work were calculated. Lateral leg swing was calculated from foot displacements.

Results: As expected, the decrease in net metabolic cost was greater, which would have been expected on the basis of the amount of weight loss. The smaller lateral leg swing after weight loss did not explain part of the decrease in net metabolic cost. The reduced body mass required less leg muscle work to raise and accelerate the COM as well as to support body weight. The decrease in body mass seems also associated with a lesser leg muscle work required to raise the COM because of smaller vertical motions. As a result of the inverted pendulum mechanism, the decrease in vertical motions (hence in potential energy fluctuations) was probably related to the decrease in mediolateral kinetic energy fluctuations. Moreover, the lesser amount of fat mass in the gynoid region seems related to the decrease in net metabolic cost of walking.

Conclusions: The reduction in net metabolic cost of walking after weight loss in weight-reduced adolescents is associated with changes in the biomechanical parameters of walking.

1Laboratory of Exercise Physiology, University of Lyon, Saint-Etienne, FRANCE; 2Laboratory of Exercise Biology (BAPS), Blaise Pascal University, Clermont-Ferrand, FRANCE; and 3Centre Médical Infantile (CMI), Romagnat, FRANCE

Address for correspondence: Nicolas Peyrot, Ph.D., Laboratoire de Physiologie del'Exercice, Médecine du Sport-Myologie, CHU Bellevue, 42055 Saint-Etienne Cedex 02, France; E-mail:

Submitted for publication October 2009.

Accepted for publication February 2010.

©2010The American College of Sports Medicine