Title :
Relating agonist-antagonist electromyograms to joint torque during isometric, quasi-isotonic, nonfatiguing contractions
Author :
Clancy, Edward A. ; Hogan, Neville
Author_Institution :
Dept. of Electr. Eng. & Comput. Sci., MIT, Cambridge, MA, USA
Abstract :
Describes an experimental study which relates simultaneous elbow flexor-extensor electromyogram (EMG) amplitude to joint torque. Investigation was limited to the case of isometric, quasi-isotonic (slowly force-varying), nonfatiguing contractions. For each of the flexor and extensor muscle groups, the model relationship between muscle group torque contribution and EMG amplitude was constrained to be a sum of basis functions which had a linear dependence on a set of fit parameters. With these constraints, the problem of identifying the EMG-to-torque relationship was reduced to a linear least squares problem. Surface EMGs from elbow flexors and extensors, and joint torque were simultaneously recorded for nonfatiguing, quasi-isotonic, isometric contractions spanning 0-50% maximum voluntary contraction. Single-/multiple-channel unwhitened/whitened/adaptively-whitened EMG amplitude processors were used to identify an EMG-to-torque relation, and then estimate joint torque based on this relation. Each unwhitened multiple-channel EMG-to-torque estimator had a standard error (SE) approximately 70% of its respective single-channel estimator. The adaptively whitened multiple-channel joint torque estimator had an SE approximately 90% of the unwhitened multiple-channel estimator, providing an estimation error ≈3% of the combined flexion/extension torque range. The experimental studies demonstrated that higher fidelity EMG amplitude processing led to improved joint torque estimation.
Keywords :
biomechanics; electromyography; medical signal processing; torque; EMG amplitude processing; EMG analysis; EMG-to-torque relation; adaptively-whitened EMG; agonist-antagonist electromyograms; elbow extensors; elbow flexors; isometric quasiisotonic nonfatiguing contractions; joint torque; maximum voluntary contraction; single-channel estimator; Amplitude estimation; Elbow; Electromyography; Least squares approximation; Least squares methods; Muscles; Road safety; Surface fitting; Surface waves; Torque measurement; Adult; Elbow Joint; Electrodes; Electromyography; Female; Humans; Isometric Contraction; Least-Squares Analysis; Male; Models, Biological; Muscles; Torque;
Journal_Title :
Biomedical Engineering, IEEE Transactions on