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Keywords:

  • grasping force;
  • hysteresis;
  • intramuscular EMG;
  • path dependency;
  • surface EMG

Abstract

Introduction:

In this study we analyzed the presence of hysteresis in the relationship between features of electromyography (EMG) and force.

Methods:

Intramuscular EMG and surface EMG (sEMG) were recorded concurrently from the flexor digitorum profundus muscle from 0% to 100% maximum voluntary contraction (MVC) in 11 subjects. Two features, mean absolute value (MAV) and Wilson amplitude (WAMP), were computed using either the first-order (poly1) or third-order (poly3) polynomial.

Results:

We detected hysteresis in the EMG–force relationship for both features in all subjects. In general, the hysteresis-based models performed better than the overall model (which does not take into account the hysteresis in the EMG–force relationship), with R2 values about 0.98 (averaged across subjects) and root mean square error around 5% of the MVC force.

Conclusion:

These results imply the existence of a path-dependent model, which may improve the accuracy of force estimation. Muscle Nerve, 2012