title: Force direction in manual wheel chair propulsion: balance between effect and cost.
abstract: OBJECTIVE
  To evaluate the relationship between mechanical effect and musculoskeletal cost in wheelchair propulsion.
  
  
  METHODS
  Simulation of force direction, based on experimental data from wheelchair users.
  
  
  METHODS
  For nine wheelchair users driving at 20 W, 1.39 m/s, the force direction was compared to simulation results based on a criterion defined as the ratio of mechanical effect and musculoskeletal cost.
  
  
  RESULTS
  Simulation data compare well to the actual force direction for the middle and final parts of the push.
  
  
  CONCLUSIONS
  The musculoskeletal cost of the exerted force must be taken into account to explain the observed propulsion pattern. Experienced users appear to optimize the force pattern by balancing mechanical effect and musculoskeletal cost of the pushing action. RelevanceThe effect-cost ratio may be a useful tool in analysing and improving wheelchair design.
authors.affiliation: Faculty of Human Movement Sciences, Vrije Universiteit, v.d. Boechorstraat 9, 1081, Amsterdam, The Netherlands.
authors.forename: L A
authors.initials: LA
authors.lastname: Rozendaal
authors.forename: D E
authors.initials: DE
authors.lastname: Veeger
mesh_terms: D001132:Arm / Q000502:physiology*; D001696:Biomechanical Phenomena; D004867:Equipment Design; D006801:Humans; D018482:Muscle, Skeletal / Q000502:physiology*; D014910:Wheelchairs