A simulation system that is capable of analyzing wheelchair propulsion using a human model which incorporates muscles and bones has been developed. The system calculates the driving force and muscular force for input movements applied to the wheelchair. In this study, three types of sitting arrangements were evaluated, namely a wheelchair in normal seat position which has no cushion, one in upward sitting position which has a seat cushion and one in forward sitting position which has a backrest cushion. This was done to determine the effect of varying the sitting position. The velocity and force applied to the driving wheel were measured by the wheelchair for propelling ability evaluation. The motion of the human body while propelling the wheelchair was captured using a three-dimensional measurement system and muscular forces were measured using the average rectified value of a surface electromyogram (ARV EMG). Measurements were performed on the following muscles: the clavicula and acromion of the deltoids, the pectoralis majors, the infraspinatus, the flexor and extensor of the carpi radialis, the biceps and the triceps. The results of the measurement were compared with the calculated muscular force. Only the acromion of the deltoids was active during the recovery phase, while the other muscles were mainly active during the drive phase of propulsion. In addition, the biceps were active in the early stage of drive phase, while the triceps were active in the latter stage. The switching point between these stages was brought forward when the sitting position was changed. The trend of the calculated muscular force variation corresponded with that of the ARV EMG.These results demonstrate the potential of the developed system. However, there were several discrepancies between the calculated and measured data. The flexor carpi radialis functioned as an agonist during the drive phase and the biceps and triceps, which are antagonist muscles, functioned alternately in the calculated results. In contrast, the biceps functioned as an agonist during the driving phase and functioned simultaneously with the triceps for some periods in the ARV EMG results.Solving these problems is remained for the future study.
