title: Mechanical work and metabolic cost of walking after weight loss in obese adolescents.
abstract: OBJECTIVE
  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.
authors.affiliation: Laboratory of Exercise Physiology, University of Lyon, Saint-Etienne, France. nicolas.peyrot@univ-st-etienne.fr
authors.forename: Nicolas
authors.initials: N
authors.lastname: Peyrot
authors.forename: Jean-Benoit
authors.initials: JB
authors.lastname: Morin
authors.forename: David
authors.initials: D
authors.lastname: Thivel
authors.forename: Laurie
authors.initials: L
authors.lastname: Isacco
authors.forename: Michel
authors.initials: M
authors.lastname: Taillardat
authors.forename: Alain
authors.initials: A
authors.lastname: Belli
authors.forename: Pascale
authors.initials: P
authors.lastname: Duche
mesh_terms: D000054:Acceleration; D000293:Adolescent; D001696:Biomechanical Phenomena; D001823:Body Composition; D015992:Body Mass Index; D002648:Child; D004734:Energy Metabolism / Q000502:physiology*; D015444:Exercise / Q000502:physiology; D006801:Humans; D007866:Leg / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology; D009765:Obesity / Q000503:physiopathology* / Q000628:therapy*; D016138:Walking / Q000502:physiology*; D015431:Weight Loss