Wheelchair sports have a tendency to depend on the performance of wheelchairs, and the weight reduction of wheelchairs made of various alloys has helped improve the performance of players. Some players have mentioned, however, that the operability and riding comfort of competition wheelchair have been affected by changing the wheelchair materials; stiffness and weight are considered to be related to operability and riding comfort. In this experiment, we installed some weights on the center of the mass of a competitive wheelchair made of magnesium alloy to be the same mass of a wheelchair made of aluminum alloy; vibrations that occurred on both wheelchairs while driving were measured and compared. The experiment was performed using 3-axis sensors. This experiment showed that the vibration frequency of the wheelchair made of magnesium alloy was different from that made of aluminum alloy. This result was thought to be influenced by the difference in Young’s modulus or the specific weight.

Currently, various types of wheelchairs for badminton have been developed for weight saving and functional improvement. The purpose of this study was to evaluate each performance of two types of competitive wheelchairs for badminton made of two different metallic materials. One of the wheelchairs used in this study was made of magnesium composite material, which was 45 GPs of Young’s modulus, 1.738 g/cm3 of the specific weight, and 9.57 kg of weight. Another was made of scandium-aluminum composite material, which was 70 GPa of Young’s modulus, 2.70 g/cm3 of the specific weight, and 10.81 kg of weight. The frames and weights of the wheelchairs were similar. In this experiment, the subject’s electromyograms from six muscles in driving each wheelchair were measured and analyzed. Furthermore, the motion in driving was captured and analyzed using a three-dimensional motion capture system. This experiment led to the following result: no significant difference was found in wheelchair performance due to the different materials.

This study examined competitive wheelchairs that facilitate sports participation. They can be moved straight ahead using only one arm. Our designed and developed competitive wheel-chairs have a dual hand-rim system. Their two hand-rims, attached to a drive wheel on one side, can be operated simultaneously for straight-ahead movement. Specifically, based on integrated electromyography (iEMG) data calculated from surface electromyography (sEMG), we examined the wheelchair loading characteristics, posture estimation, and effects on body posture during one-arm propulsion movement. The first experiment yielded insights into arm and shoulder-joint muscle activation from iEMG results obtained for two-hand propulsion and dual hand-rim system propulsion. Results suggest that muscle activation of one arm can produce equal propulsive force to that produced by two arms. The second experiment estimated the movement posture from iEMG during one-arm wheelchair propulsion. The external oblique abdominis is particularly important for one-arm wheelchair propulsion. The iEMG posture estimation validity was verified based on changes in the user body axis and seat pressure distribution. In conclusion, as confirmed by iEMG, which is useful to estimate posture during movement, one-arm wheelchair use requires different muscle activation sites and posture than when using two arms.

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