Handgrip Force Estimation Based on a Method Using Surface Electromyography (sEMG) of Extensor Carpi Radialis Longus

Both flexor and extensor muscle activated together when hand-grip task conducted, but there is little work that attempts to specifically investigate the relationship of the hand-grip force level and the EMG activity of extensor muscles. The present study was designed to investigate the correlation between hand-grip force level and sEMG of ECRL (extensor carpi radialis longus, ECRL). A pseudo-randomized sequence of hand-grip tasks with some specific force ranges has been defined for calibration. Eight subjects (university students, five males and three females) were recruited to conduct both calibration trials and voluntary trials. EMG signals have been preprocessed with RMS (root-mean-square) method, after which EMG signals are normalized with amplitude value of MVC-related EMG. With data regression of calibration trials, a linear model has been developed to correlate the handgrip force output with sEMG activities of ECRL and this linear model then is employed to estimate the hand-grip force production of voluntary trials. The root-mean-square-error (RMSE) of the estimated force output for all the voluntary trials are statistically compared in different force ranges. The results indicate that the linear model is useful to estimate the handgrip force based on the EMG activities of forearm extensor muscle, and the accuracy of this model is dependent on the force levels. That is the linear model can provide best estimation in moderate force range (30%-50% MVC), while the force prediction error tends to be large for weak force (20%-30% MVC) or strong force (50%-80% MVC).