ESTIMATION OF MUSCLE FORCES ABOUT THE WRIST JOINT DURING ISOMETRIC TASKS USING AN EMG COEFFICIENT METHOD

A technique for estimating isometric muscle forces based on EMGs and a natomical parameters is presented. In the present study, we record EMG s from five muscles acting at the wrist, during a series of isometric contractions in flexion, extension, ulnar deviation and radial deviati on. The method then uses these EMG signals and the necessary anatomica l data to estimate individual muscle forces. For one subject, complete anatomical parameters were estimated by MRI reconstruction of muscle moment arms and lines of muscle action. In all subjects, the errors as sociated with variability in the EMG signals were reduced through the use of signal processing techniques and intensive subject training. Th ese EMG-based force estimates were then validated by evaluations at to rque directions in which no mechanical redundancy existed. The stabili ty of the solution space was examined using Monte Carlo simulations. T he results of our study show that individual muscle forces at the wris t can be estimated with considerable accuracy, without assuming any co ntrol strategy (as is done with optimization theories). However, due t o the limited mechanical redundancy of the wrist, it is uncertain whet her the method can be used to estimate muscle forces in more highly re dundant systems.