Evaluation of handgrip force from EMG measurements

A series of experiments were performed in order to investigate whether estimates of handgrip force could be derived with fair accuracy from surface EMG levels recorded on the finger flexors of the forearm, taking into account the position of the wrist in the flexion-extension plane and in the ulnar-radial deviation plane. Handgrip forces (on a JAMAR dynamometer) and corresponding surface EMG levels (on the finger flexors of the forearm) were recorded for 20 subjects in 11 postures of the wrist and for 30% and 70% of the MVC in neutral posture. A mathematical empirical model was developed using multiple non-linear regression analysis. Although quite simple, it provides very reliable results, the correlation coefficient between predicted and observed forces being 0.895. Its use must, however, be restricted to work situations where: (a) the hand efforts are of the same type and involve the same muscles as those exerted on the dynamometer; (b) the hand is in neutral pro-supination; and (c) no voluntary effort is exerted by the wrist flexors except for maintaining the wrist posture.