Perceived discomfort of shoulder and elbow postures with external loads

The objective of this study is to investigate the perceived discomfort for the external load added postures which are combined with shoulder flexion/extension and elbow flexion. 12 healthy male undergraduate and graduate students participated in this experiment. Independent variables were the shoulder flexion/extension angle (-20°, 0, 45°, 90°, 135°), the elbow flexion angle (0, 45°, 120°), and the external load (0, 1.5Kg, 3Kg). Dependent variable was a whole body perceived discomfort using Borg's CR10. The subjects rated the perceived discomfort after they had maintained the given posture for 60 seconds. The ANOVA results showed that main factors and three two-way interactions were statistically significant at α=0.05. The regression analyses were performed to quantify the effect of external loads on the perceived discomfort. The perceived discomfort linearly increased as the external loads increased. The effect of the external loads to the perceived discomfort was quantified and classified into three levels based on the result of regression analyses.