Posture Estimation Using Surface Electromyography during Wheelchair Hand-Rim Operations

Abstract

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.

Keywords: assistive technology; competitive wheelchair; iEMG; muscle activation; parasports; sEMG; seat pressure.

Figure 1

Competitive wheelchair with the dual hand-rim system: (a) right-hand drive with a camber angle, (b) left-hand drive without a camber angle, and (c) a double-ring drive shaft structure.

Figure 2

Measurement position of sEMG and schematic diagram I: (a) five measurement points and (b) schematic diagram of the experiment.

Figure 3

Posture of research participants under loading: (a) posture of research participants holding the dumbbells Part 1 and (b) posture of research participants holding the dumbbells Part 2.

Figure 4

Measurement position of sEMG and schematic diagram II: (a) three measurement points and (b) schematic diagram showing the experiment.

Figure 5

iEMG calculation results for eight strokes performed with one-arm and two-arm driving: (a) flexor digitorum profundus (pinky side), (b) triceps brachii, (c) deltoid, (d) pectoralis major, and (e) latissimus dorsi.

Figure 5

iEMG calculation results for eight strokes performed with one-arm and two-arm driving: (a) flexor digitorum profundus (pinky side), (b) triceps brachii, (c) deltoid, (d) pectoralis major, and (e) latissimus dorsi.

Figure 6

Distribution of iEMG results obtained at each muscle site with one-arm and two-arm driving.

Figure 7

iEMG calculation results for eight strokes during one-arm and two-arm driving: (a) erector spinae, (b) external oblique abdominis, and (c) triceps brachii.

Figure 8

Distribution of iEMG results obtained at each muscle site with one-arm and two-arm driving (by left and right side).

Figure 9

Body axis change results obtained for one-arm and two-arm driving for eight repetitions: (a) X-axis, (b) Y-axis, and (c) Z-axis.

Figure 10

Different seat pressure distribution values for the nine segments: (a) an example of a heat map at rest, (b) the difference results for seat pressure distribution.