Perception of shoulder muscular effort during low-demand load transfer tasks

This study focused on quantifying the mathematical relationship between shoulder physical loading and muscular effort perception during low physical demand tasks. Subjects underwent training to calibrate to their range of shoulder strength capability. Subjects transferred visually identical bottles representing specified percentages of extended arm maximal voluntary force (MVF) in defined azimuth directions to identified targets. They then reported their percentage of perceived shoulder exertion relative to their calibrated range. Measures of physical shoulder loading were calculated from experimental data with a dynamic shoulder moment model. Shoulder reported perceived muscular exertion (RPE) values were most significantly correlated with percent MVF (r = 0.81), suggesting subjects were influenced more by the manipulated hand load than the shoulder-specific physical load. Multiple regression analyses demonstrated that other personal and task factors influenced shoulder RPE. Generally, subjects overestimated shoulder physical loading, and the quality of their perception degraded as the load increased.