Assessing manual wheelchair caster design for mobility in winter conditions.

Wheelchair users who live in cold climates are faced with daily difficulties related to personal independence and societal inclusion as their assistive devices are unable to overcome the physical barriers created by snow and ice. The purpose of the research was to evaluate four commercially available casters to determine which caster performed best on snow-covered surfaces. Performance measures included: travel time, force transfer through the palms of the hands, number of propulsive movements, static resistance to movement, kinetic resistance to movement, and caster penetration into the packed snow. On a snow-covered incline, the FreeWheel™ caster enabled travel time to be decreased by 10 s, requiring 3 fewer propulsive movements and 60% of the amount of force to propel the wheelchair compared with solid casters. Static and kinetic resistance tests did not differentiate the four caster types. Penetration into packed snow was reduced from 11.9 mm to approximately 1 mm by changing from solid casters to the FreeWheel™ or Wheelblades™ caster types on flat surfaces. Similar results were observed on a snow-covered incline for the Wheelblades™, however, the FreeWheel™ penetrated approximately 8 mm. Considering the entire body of evidence, the FreeWheel™ performed the best on snow-covered surfaces.