Biomechanical comparison of two racing wheelchair propulsion techniques.

PURPOSE: The purpose was to compare the conventional (CVT) and para-backhand (PBT) techniques used for racing wheelchair propulsion. Selected 3-D kinematic characteristics of the upper body and the electromyographic (EMG) signals of selected muscles during racing wheelchair propulsion over a roller system were examined.
METHODS: Eight CVT and seven PBT elite performers served as the subjects. Each subject performed maximum effort pushing for 30 s at a load that simulated overground pushing. Two S-VHS camcorders (60 Hz) were used to obtain 3-D kinematic parameters and muscle activity was monitored using surface electrodes.
RESULTS: The CVT was found to have significant shorter push time, smaller relative push time, and greater relative recovery time than the PBT. The CVT is a more compact stroke (smaller joint range of motion) and the PBT has a faster overall movement speed. Significant differences in arm positions were found between the two techniques at the instants of hand contact and hand release, and the upper arm was more internally rotated at these two instants in the CVT when compared with the PBT. The EMG data showed that large variations in muscle activation patterns existed in each technique group. In general, the flexor carpi radialis and triceps brachii were most active in the push phase. The upper trapezius and postero-middle deltoids were most active in the ascending recovery phase, whereas the extensor carpi radialis, biceps brachii, antero-middle deltoids, and pectoralis major were most active during the descending recovery phase.
CONCLUSIONS: The greater push time and push angle associated with the PBT suggest that the PBT may be more suitable for endurance athletes who are less explosive in their pushing strokes. The greater time and angle allow PBT users the opportunity to transmit more force to the wheel.