A new method to estimate signal cancellation in the human maximal M-wave.
A new method is introduced that estimates EMG signal cancellation in surface recorded investigations. Its usefulness is demonstrated when determining changes in the maximal motor response (M-wave) magnitude during rest and voluntary contraction. The accuracy of recording and analysis methods and the reliability of the maximal M-wave were assessed in the human gastrocnemius and soleus. The maximal M-wave was recorded by bipolar surface electrodes placed 2 cm, 3 cm and 4 cm apart, and by monopolar (one active and one indifferent reference) surface electrodes. Up to 85% of the maximal M-wave was lost due to signal cancellation during bipolar recording. The maximal M-wave magnitude decreased consistently and significantly during triceps surae contraction compared to rest when recorded by monopolar electrodes, but not when recorded by bipolar electrodes. Area and peak-to-peak (PTP) amplitude analysis methods provided similar results when determining the magnitude of the maximal M-wave. This provides evidence that monopolar recording is superior to bipolar recording as it removes the signal cancellation error and allows the genuine changes in maximal M-wave magnitude to be observed.
Tucker
K J
KJ
Discipline of Physiology, School of Molecular and Biomedical Sciences, University of Adelaide, SA 5005, Australia.
Türker
K S
KS
D000200:Action Potentials / Q000502:physiology*; D000328:Adult; D000465:Algorithms; D001369:Axons / Q000502:physiology; D003936:Diagnosis, Computer-Assisted / Q000379:methods*; D004558:Electric Stimulation; D004576:Electromyography / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D009046:Motor Neurons / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D018482:Muscle, Skeletal / Q000294:innervation / Q000502:physiology*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity