title: Metabolic and mechanical energy costs of reducing vertical center of mass movement during gait.
abstract: OBJECTIVE
  To test the hypothesis that reducing vertical center of mass (COM) displacement will lower the metabolic cost of human walking. To examine changes in joint work associated with increasing and decreasing vertical COM movement during gait.
  
  
  METHODS
  Randomized repeated measures.
  
  
  METHODS
  Human Neuromechanics Laboratory, University of Michigan.
  
  
  METHODS
  Able-bodied subjects (N=10).
  
  
  METHODS
  Subjects walked at 1.2m/s on a treadmill and overground. Subjects manipulated vertical COM displacement either by adjusting stride length or by using visual feedback to reduce COM movement.
  
  
  METHODS
  We measured kinematic and kinetic data to calculate vertical and lateral COM displacements, joint torques, and work. In addition, we collected oxygen consumption to calculated metabolic power.
  
  
  RESULTS
  Increasing and decreasing vertical COM displacement beyond subjects' preferred range resulted in increases in the metabolic cost of walking. When vertical COM displacement was reduced, corresponding increases in positive ankle and hip work and negative knee work were observed.
  
  
  CONCLUSIONS
  Humans are capable of walking in a manner that will reduce COM displacement from normal. Decreasing vertical COM movement results in increases in metabolic energy costs because of greater mechanical work performed at the hip, knee, and ankle joints. Thus, reducing vertical COM movement is not a successful strategy for improving either metabolic or mechanical energy economy during normal walking by able-bodied subjects.
authors.affiliation: Department of Movement Science, University of Michigan, Ann Arbor, MI, USA. keith-gordon@northwestern.edu
authors.forename: Keith E
authors.initials: KE
authors.lastname: Gordon
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Ferris
authors.forename: Arthur D
authors.initials: AD
authors.lastname: Kuo
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology*; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D005684:Gait / Q000502:physiology*; D006801:Humans; D008297:Male; D010101:Oxygen Consumption; D016138:Walking / Q000502:physiology