title: The influence of wheelchair propulsion technique on upper extremity muscle demand: a simulation study.
abstract: BACKGROUND
  The majority of manual wheelchair users will experience upper extremity injuries or pain, in part due to the high force requirements, repetitive motion and extreme joint postures associated with wheelchair propulsion. Recent studies have identified cadence, contact angle and peak force as important factors for reducing upper extremity demand during propulsion. However, studies often make comparisons between populations (e.g., able-bodied vs. paraplegic) or do not investigate specific measures of upper extremity demand. The purpose of this study was to use a musculoskeletal model and forward dynamics simulations of wheelchair propulsion to investigate how altering cadence, peak force and contact angle influence individual muscle demand.
  
  
  METHODS
  Forward dynamics simulations of wheelchair propulsion were generated to emulate group-averaged experimental data during four conditions: 1) self-selected propulsion technique, and while 2) minimizing cadence, 3) maximizing contact angle, and 4) minimizing peak force using biofeedback. Simulations were used to determine individual muscle mechanical power and stress as measures of muscle demand.
  
  
  RESULTS
  Minimizing peak force and cadence had the lowest muscle power requirements. However, minimizing peak force increased cadence and recovery power, while minimizing cadence increased average muscle stress. Maximizing contact angle increased muscle stress and had the highest muscle power requirements.
  
  
  CONCLUSIONS
  Minimizing cadence appears to have the most potential for reducing muscle demand and fatigue, which could decrease upper extremity injuries and pain. However, altering any of these variables to extreme values appears to be less effective; instead small to moderate changes may better reduce overall muscle demand.
authors: Department of Mechanical Engineering, The University of Texas at Austin, Austin, TX, USA.
authors: Jeffery W
authors: JW
authors: Rankin
authors: Andrew M
authors: AM
authors: Kwarciak
authors: W Mark
authors: WM
authors: Richter
authors: Richard R
authors: RR
authors: Neptune
mesh_terms: D000328:Adult; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008297:Male; D008328:Man-Machine Systems; D008875:Middle Aged; D008954:Models, Biological; D009119:Muscle Contraction; D018482:Muscle, Skeletal / Q000503:physiopathology*; D005082:Physical Exertion; D011597:Psychomotor Performance; D034941:Upper Extremity / Q000503:physiopathology*; D014910:Wheelchairs