title: Predicting non-isometric fatigue induced by electrical stimulation pulse trains as a function of pulse duration.
abstract: BACKGROUND
  Our previous model of the non-isometric muscle fatigue that occurs during repetitive functional electrical stimulation included models of force, motion, and fatigue and accounted for applied load but not stimulation pulse duration. Our objectives were to: 1) further develop, 2) validate, and 3) present outcome measures for a non-isometric fatigue model that can predict the effect of a range of pulse durations on muscle fatigue.
  
  
  METHODS
  A computer-controlled stimulator sent electrical pulses to electrodes on the thighs of 25 able-bodied human subjects. Isometric and non-isometric non-fatiguing and fatiguing knee torques and/or angles were measured. Pulse duration (170-600 μs) was the independent variable. Measurements were divided into parameter identification and model validation subsets.
  
  
  RESULTS
  The fatigue model was simplified by removing two of three non-isometric parameters. The third remained a function of other model parameters. Between 66% and 77% of the variability in the angle measurements was explained by the new model.
  
  
  CONCLUSIONS
  Muscle fatigue in response to different stimulation pulse durations can be predicted during non-isometric repetitive contractions.
authors: Biomedical Engineering Program, University of California, Davis, CA 95616, USA. sumerian@udel.edu
authors: M Susan
authors: MS
authors: Marion
authors: Anthony S
authors: AS
authors: Wexler
authors: Maury L
authors: ML
authors: Hull
mesh_terms: D000328:Adult; D000465:Algorithms; D001696:Biomechanical Phenomena / Q000502:physiology; D003198:Computer Simulation; D004558:Electric Stimulation / Q000379:methods*; D004566:Electrodes; D005260:Female; D006801:Humans; D007537:Isometric Contraction / Q000502:physiology; D007866:Leg / Q000033:anatomy & histology / Q000502:physiology; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D009119:Muscle Contraction / Q000502:physiology; D018763:Muscle Fatigue / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012984:Software; D013848:Thigh / Q000502:physiology; D055815:Young Adult
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