Comparisons of Three-Dimensional Pushrim Forces during Three Racing Speeds of Wheelchair Propulsion

Abstract

Although pushrim kinematics of racing wheelchair propulsions (RWP) has been widely investigated, pushrim kinetics is very limited due to the complexity of pushrim force measurement device. At present, only one study explored pushrim kinetics and reported the tangential and axial forces during RWP. PURPOSE: To determine the three-dimensional (3-D) pushrim forces and compared the pushrim forces during RWP among three different propulsive speeds METHODS: Five experienced male wheelchair racers who classified as T52-T54, mean age of 28.4 (6.87) years, volunteered for this study. Kinetic data were obtained from an instrumented wheel system which incorporated JR-3 force transducer attached to the right wheel axle. Three retroreflective markers were placed on the right side of second metacarpophalangeal joint, the fifth metacarpophalangeal joint, and the midpoint between radial and ulna styloid processes. Two retroreflective markers were placed on the wheel in order to obtain wheel angular positions. Six 120-Hz optical cameras were used to acquire kinematics data. Both kinematics and kinetics data were collected synchronously at 90%, 70%, and 50% of the maximum RWP speeds on a roller system. Three trials were recorded on each speed conditions with a duration of 30 seconds for each trial. The Friedman test was employed to determine the different pushrim forces for the three speed conditions. RESULTS: Among the generated 3-D pushrim forces, peak radial force was the highest force on all speed conditions. The peak radial forces of 50%, 70%, and 90% of RWP were 104.6 N, 123.5 N and 136 N respectively. These peak radial forces were significantly increased from 50% to 70%, and from 70% to 90% speed conditions (p<0.05). CONCLUSIONS: As propulsive speed increases, all pushrim forces (the tangential, radial, and axial forces) increase. Radial force was found to be the greatest force and increased significantly which may lead to potential joint injuries of upper extremities.