Biomechanics of racing wheelchair propulsion: Development of an instrumented wheel force measurement system and its applications

It has been known that biomechanical studies can gain insight of the causes and consequences of high loads on upper extremities during wheelchair propulsion. However, this information is limited for racing wheelchair propulsion (RWP) due to lack of reliable devices to measure pushrim forces. Therefore, the purpose of this dissertation is to develop an instrumented wheel force system (IWS) that can measure three-dimensional (3-D) pushrim forces during RWP as well as its application for determining the effect of propulsive speeds on shoulder joint forces (SHJF).; The first part of the study dealt a mechanical design and validation of the IWS. The results showed that the IWS could be used to measure 3-D pushrim forces with high linearity and coefficient of determination for both static and dynamic validation. The highest percent error was found to be 4.3% during dynamic validation. The second part involved development of a software program to quantify upper extremity JF and JM via an inverse dynamic model. An experienced wheelchair racer volunteered to propel a standard racing wheelchair (SRW) equipped with the IWS. The SRW was secured on a stationary wheelchair roller. Kinematic data were obtained from six 120 Hz cameras, while kinetic data were collected at a sampling rate of 600 Hz. Both systems were synchronized via the Peak Performance Motion Analysis System. Spatial and temporal characteristics of RWP as well as JF and JM of upper extremity joints were reported.; The last part investigated the effect of propulsive speeds on SHJF. Five experienced wheelchair athletes propelled the SRW equipped with the IWS at 3 different speeds (50%, 70% and 90% of an individual's maximum speed) on a wheelchair roller. Kinetic and kinematic data were recorded for 30 seconds when athletes reached and maintained +/-5% of the target speed. Three trials were collected for each speed condition. A Friedman test revealed differences of SHJFs between speed conditions (p<0.000). A series of Wilcoxon Sign-Rank tests showed significant differences of the mean and peak SHJF for all pairwises. The results showed that SHJFs increased as speed increased. The forces directed in inferior and anterior directions were the most dominant forces. The combination of these high loads may predispose the wheelchair racers to the shoulder injury.