An estimated 3.26 million manual wheelchair users (MWUs) exist in the United States . MWUs report a high incidence of upper extremity joint pain largely attributed to wheelchair propulsion, which exposes the upper limbs to high forces and torques repetitively over time . There exists a clear need for assistive wheelchair technologies capable of reducing the loads experienced by the upper extremity joints during propulsion.
IntelliWheels, Inc. has developed multi-geared wheel systems, including both low and high gear systems, where a planetary gear train connects the wheel hub to the wheel hand rim. Decreasing gear ratio, we hypothesize, may reduce the forces and torques required by the user during propulsion. To evaluate this claim, we constructed and validated an instrumented wheelchair hand rim system capable of use on either geared or standard wheelchair wheels. Commercially available devices exist to perform wheelchair kinetics, such as the SmartWheel (SW) (Three River Holdings LLC; Mesa, AZ, USA), however, these devices require the use of a manufacturer specified wheel. As a result, a custom solution was required to interface with the geared wheels used in this study.