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Keywords:

  • adaptive whitening;
  • extreme high pass filtering;
  • fatigue;
  • neural tension-limiting mechanism;
  • surface electromyography

ABSTRACT

Introduction: Surface electromyography (sEMG) amplitude increases with constant muscle tension during fatiguing sub-maximum efforts. The purpose of this study was to determine if extreme highpass filtering and/or autoregressive whitening would result in a more consistent sEMG-to-moment ratio than a standard bandpass filter (20–500 Hz) during repeated, dynamic maximal efforts of the quadriceps. Methods: We collected sEMG and knee extensor moment from 16 participants during the concentric and eccentric phases of repeated, maximal knee extensor efforts. Results: The alternative processing methods provided more consistent vastus medialis and lateralis sEMG-to-moment ratios. A neural tension-limiting mechanism appeared to exist and was magnified during the eccentric phase, particularly with fatigue. Conclusions: There appears to be a difference in how the central nervous system controls concentric and eccentric efforts as the quadriceps fatigues, and this is more apparent with the alternative EMG processing methods we used. Muscle Nerve 50: 384–392, 2014