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.
Keywords: adaptive whitening; extreme high pass filtering; fatigue; neural tension-limiting mechanism; surface electromyography.
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