Comfort Evaluation of the Range of Motion of Human Upper Limb Joints

To evaluate the discomfort degree of upper limb joint motions, the experiment with external load was carried out based on subjective feeling scale and sEMG signal analysis. Eleven university students participated the experiment. the data of subjective feeling of comfort and the sEMG of the related muscle of shoulder joint (forward extension, rear protraction, adduction, abduction, flex level, stretch level), elbow joint (flexion), wrist joint (palmar flexion, dorsal flexion, and ulnar flexion) and ulnar radial joints (pronation and supination) with 1 kg of loads. Each joint movement was parted into 4 range (25% ROM, 50% ROM, 75% ROM, 100% ROM) to collect the above data. The results showed that the subjective comfort is related to the joint type, joint movement, joint movement angle and other factors. Under the effect of external load, the highest degree of discomfort was horizontal extension of shoulder joint, followed by dorsal flexion of wrist joint; Elbow flexion was the most comfortable, followed by shoulder forward extension and horizontal flexion. The sEmg data could more sensitively reflect the change of human discomfort than subjective sensation, among which IEMG value was a better indicator.