European Journal of Applied Physiology

, Volume 107, Issue 2, pp 177–185 | Cite as

Relationships between surface EMG variables and motor unit firing rates

  • Anita Christie
  • J. Greig Inglis
  • Gary Kamen
  • David A. Gabriel
Original Article
First Online:
Accepted:

Abstract

Although surface electromyography (sEMG) is a widely used electrophysiological technique, its physiological interpretation remains somewhat controversial. This study examined the relationship between motor unit firing rates (MUFR) and the root mean square (RMS) amplitude and mean power frequency (MPF) of the sEMG signal in the biceps brachii. Eleven subjects performed maximal isometric elbow flexion while indwelling and sEMG recordings were obtained from the biceps. The RMS amplitude and MPF of the surface signal, and the mean MUFR from the indwelling signal, were calculated over 500 ms epochs. Group means showed a strong MUFR–RMS amplitude relationship (r 2 = 0.91), but a weak MUFR–MPF relationship (r 2 = 0.20). Using all trials, the MUFR–RMS amplitude (r 2 = 0.19) and MUFR–MPF (r 2 = 0.0037) relationships were much weaker. Within individual subjects, the MUFR–RMS amplitude (mean r 2 = 0.13 ± 0.17) and the MUFR–MPF (mean r 2 = 0.040 ± 0.041) relationships were also weak. These results suggest that MUFR cannot be predicted from the characteristics of the sEMG signal.

Keywords

Ramp contraction Amplitude and frequency analysis Isometric contraction Indwelling EMG 
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Notes

Acknowledgments

This project was supported by a grant from the Natural Sciences and Engineering Research Council (NSERC) of Canada, awarded to D.A. Gabriel.

Supplementary material

421_2009_1113_MOESM1_ESM.doc (44 kb)
Supplementary material 1 (DOC 44 kb)

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Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Anita Christie
    • 1
  • J. Greig Inglis
    • 2
  • Gary Kamen
    • 1
  • David A. Gabriel
    • 2
  1. 1.Department of KinesiologyUniversity of MassachusettsAmherstUSA
  2. 2.Department of Physical Education and KinesiologyBrock UniversitySt. CatharinesCanada

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