title: Relationship between resultant force at the pushrim and the net shoulder joint moments during manual wheelchair propulsion in elderly persons.
abstract: OBJECTIVE
  To determine the relationship between the resultant force at the pushrim and the net shoulder joint moments during manual wheelchair propulsion in elderly persons.
  
  
  METHODS
  Convenience sample.
  
  
  METHODS
  Motion analysis laboratory.
  
  
  METHODS
  Older manual wheelchair users (N=14; age, 68.2+/-5.2y) were tested.
  
  
  METHODS
  Kinematic and kinetic data were collected during manual wheelchair propulsion at a speed between 0.96 and 1.01m/s for 10 seconds and at a power output around 22.4W on a wheelchair ergometer.
  
  
  METHODS
  Net shoulder joint moments were computed with an inverse dynamic model. The mechanical use of the forces at the pushrim and the mechanical fraction of effective force were measured during propulsion.
  
  
  RESULTS
  Mechanical use and mechanical fraction of effective force had a positive and significant correlation with the net internal (P<.05) and external (P<.001) shoulder rotation moment, the net flexion (P<.05), and extension (P<.001) moment in the sagittal plane, and the net flexion (P<.001) moment in the horizontal plane.
  
  
  CONCLUSIONS
  The results suggest that because the resultant force at the pushrim has a greater tangential component and a greater proportion of the maximal voluntary force, most of the net moments around the shoulder are higher. Thus the optimal way of propelling, from a mechanical point of view (ie, tangential), may not be advantageous for manual wheelchair users.
authors.affiliation: Laboratoire de Recherche en Imagerie et Orthopédie, CRCHUM, Hôpital Notre-Dame, Montréal, QC, Canada. guillaume.desroches.1@ens.etsmtl.ca
authors.forename: Guillaume
authors.initials: G
authors.lastname: Desroches
authors.forename: Rachid
authors.initials: R
authors.lastname: Aissaoui
authors.forename: Daniel
authors.initials: D
authors.lastname: Bourbonnais
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D055592:Biophysical Phenomena; D001703:Biophysics; D016552:Ergometry; D005260:Female; D006801:Humans; D008297:Male; D008954:Models, Biological; D009068:Movement / Q000502:physiology*; D012785:Shoulder Joint / Q000502:physiology*; D014910:Wheelchairs