Ranking systems for evaluation of joint and joint motion stressfulness based on perceived discomforts.

This study aims to develop ranking systems for evaluation of the stressfulness of joints and joint motions based on perceived discomforts measured through an experiment. Twenty healthy male subjects participated in the experiment, where discomforts for varying joint motions in the sitting and standing postures were measured using the magnitude estimation. The results showed that the perceived discomforts were affected by the type of joint motions, size of joint motions, and joints. The joints and joint motions were classified into several distinct classes according to perceived stresses. Three ranking systems based on the perceived discomforts were developed, including classification by the joint motions and joints, by types of joint motions, and by the joints only. The ranking systems revealed that while hip and back motions exhibited higher discomfort ratings than any other joint motion, elbow motions were the least stressful of all joint motions. The ranking systems can be used as a valuable design guideline when ergonomically designing or evaluating workplaces, or as a helpful tool for understanding adverse effects of poor working postures.