Electromyographic Assessments of Muscle Activation Patterns During Driving a Power Wheelchair

Power wheelchairs are essential for cerebral palsy children with mobility impairments. The purpose of this study was to establish a muscles sequence pattern of the upper limbs to help clinicians determine a child's readiness to control the joystick for maneuvering a power wheelchair. Five individuals performed four joystick control tasks, including forward, backward, left-turn, and right-turn. The X/Y positions of joystick and surface electromyographic (EMG) signals were record simultaneously. The surface EMG was used to record the contraction of four right upper limbs muscles, including extensor carpi ulnaris (ECU), extensor carpi radialis (ECR), pronator teres (PNT), and deltoid anterior (DA). A technique for analyzing and comparing the dynamic patterns of EMG collected during driving a power wheelchair was presented. Driving EMG patterns were computed to consist of both magnitude (amplitude) and phase (timing) components. For the magnitude component, the magnitude component of the EMG patterns is defined as the muscle during rest, slight contraction, or forceful contraction. The phase component of the EMG patterns is defined as the muscles of contraction duration with active or inactive regions in each joystick control task. The results showed that participants use more muscle efforts of the ECU and ECR compared to PNT and DA during four joystick control tasks. The active regions of the phase component were similar between the ECU and ECR. There were more phase component of forceful muscle contraction of the ECU compared to ECR during left-turn task. PNT muscles did not contract during the right-turn task. DA muscles were only slight contraction during the forward task. The findings imply that the joystick control strategy for power wheelchairs may be profiled by the muscle sequence patterns of the wheelchair users.