title: Relating agonist-antagonist electromyograms to joint torque during isometric, quasi-isotonic, nonfatiguing contractions.
abstract: This paper 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 EMG's 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 approximately 3% of the combined flexion/extension torque range. The experimental studies demonstrated that higher fidelity EMG amplitude processing led to improved joint torque estimation.
authors.affiliation: Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge 02139, USA. msmail5.clancye@tsod.lmig.com
authors.forename: E A
authors.initials: EA
authors.lastname: Clancy
authors.forename: N
authors.initials: N
authors.lastname: Hogan
mesh_terms: D000328:Adult; D004551:Elbow Joint / Q000502:physiology*; D004566:Electrodes; D004576:Electromyography / Q000295:instrumentation / Q000379:methods* / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology*; D016018:Least-Squares Analysis; D008297:Male; D008954:Models, Biological; D009132:Muscles / Q000502:physiology*; D019415:Torque