Effect of Segmental Velocity Increments On Maximum Wheelchair Racing Speed

Abstract

PURPOSE: Biomechanical characteristics in wheelchair propulsion such as range of motions, segment velocities and accelerations, and pushrim forces and moments have been broadly documented; however, the effect of segmental velocities on wheelchair racing have not been investigated. This study was to determine the effect of linear segmental velocity increments of the upper extremity on the maximum wheel speed (MWS) in wheelchair racing. METHODS: Seventeen elite international wheelchair racers with the mean age of 30.3 ± 7.0 yrs, body mass 57.5 ± 10.2 kg and wheelchair racing training 8.9 ± 6.6 yrs served as participants. Reflective markers were placed on right 5th metacarpal head (hand), lateral styloid process (wrist), lateral epicondyle of the humerus (elbow) and acromion (shoulder), as well as the right wheel. Participants were filmed at 100Hz by a three-dimensional motion system while propelling their own racing wheelchairs on a training roller at their maximum speeds. After shoulder, elbow, wrist and hand linear velocities in the drive phase were calculated, linear segmental velocity increments were derived based on the difference of peak linear velocities between two adjacent joints, including shoulder-to-elbow (SE), elbow-to-wrist (EW) and wrist-to-hand (WH) velocity increments. A multiple linear regression was employed to determine the effect of each increment on the MWS. RESULTS: Mean peak linear velocities were 2.04 ± 0.38 m/s for the shoulder, 5.14 ± 0.83 m/s for the elbow, 6.26 ± 1.15 m/s for the wrist and 7.53 ± 1.03 m/s for the hand. The mean MWS was 9.14 ± 1.72 m/s. Peak linear velocities increased from proximal to distal joints, specifically from shoulder to the elbow (from 2.04 to 5.14 m/s). It was shown 87% of the variance of the MWS was accounted for by segmental velocity increments (P < 0.01) with the greatest contribution from WH and the least contribution from EW (MWS = -21.92 + 1.67SE + 1.42EW + 2.02WH). CONCLUSIONS: It is speculated that increasing wrist linear velocity by performing more abduction/addition in the drive phase may improve the wheelchair racing speed. Supported by the Roosevelt Warm Springs Institute for Rehabilitation, Warm Springs, GA