Discomfort evaluation of upper limb joint motion

Objective: To evaluate discomfort of upper limb joint motion and study the relationship between surface Electromyography (sEMG) and discomfort of upper limb joint motion.

Method: Twelve undergraduate participated the experiment. Twelve upper limb joint motions were evaluated based on perceived discomfort combined with the measurement of sEMG. Four magnitudes which they were 25%, 50%, 75%, 100% of each joint motion was evaluated. The discomfort index was defined to compare the discomfort of different joint.

Results: Perceived discomfort was affected by the joints, type of joint motions, and angle of motion. There was a trend that the perceived discomfort increased with the increasing of the degree of joint motion and the elbow flexion was the most comfort joint motion while the shoulder extension in horizontal plane was the most discomfort. The result of sEMG indicated that the parameters of root mean square (RMS) and integrated electromyography (IEMG) were sensitive to joint motion.

Conclusion: Measurements of sEMG is a better way to evaluate pepole's discomfort of joint motion than perceived discomfort. The method and results of this study can provide reference and guidance to the comfort evaluation of ergonomics of upper limb performance.