The Effects of Posture on Force Estimations Using Surface Electromyography

Abstract

Surface electromyography (sEMG) has shown promise in estimating grip forces while people are performing tasks; however, equipment and analysis procedures remain complex for use by practitioners in industry. The objective of this study was to quantify error in grip force estimations associated with changes in hand/wrist posture using simple methods and off-the-shelf sEMG equipment. Eight healthy, college-aged females participated in the study. Six sEMG sensors were placed radially around the forearm. Subjects applied 15%, 45%, and 75% of maximum power grip strength in seven different postures (neutral, 15, 30, and 45 degrees extension, and 15, 30, and 45 degrees flexion). sEMG signals were calibrated using linear regression and used to predict grip force. Predicted grip force was statistically compared to applied grip force measured by a digital dynamometer. The results suggest that radial electrode placement can generate reasonably accurate static force estimations regardless of MVC and across most postures, but extreme posture estimations do not appear accurate without corrections.