An instrumented wheel system for measuring 3-D pushrim kinetics during racing wheelchair propulsion.

The purpose of this study was to design and validate an instrumented wheel system (IWS) that can measure 3-dimensional (3-D) pushrim forces during racing wheelchair propulsion. Linearity, precision, and percent error were determined for both static and dynamic conditions. For the static condition, the IWS demonstrated a high linearity (0.91 <or= slope <or= 1.41) with less than 2.72% error rate. Under dynamic loading, the IWS provided the well-matched measurement forces with the predicted values from the inverse dynamics method (0.96 <or= slope <or= 1.07) with less than 4.32% error rate. The results revealed that the IWS developed in the study can be used to measure 3-D pushrim reaction forces with acceptable accuracy. This was the first instrumented wheel device that can register 3-D pushrim forces during racing wheelchair propulsion. With the available kinetic information of the 3-D pushrim forces, the upper extremity joint reaction forces could be determined.