Tonic and kinetic motor units revisited: Does motor unit firing behavior differentiate motor units?

Yoshihisa Masakado, Kazuto Akaboshi, Akio Kimura, Naoichi Chino

Research output: Contribution to journalArticle

1 Citation (Scopus)


Objective: We tried to differentiate motor unit into two distinct populations, tonic and kinetic, on the basis of the relationship between the mean inter-spike interval and its variability. Methods: During voluntary isometric contraction myoelectric activity was recorded with a special quadrifilar electrode from first dorsal interosseous, biceps brachii, soleus, and tibialis anterior muscle. Motor unit action potentials (MUAP) were decomposed into individual MUAP trains, by electromyography (EMG) signal decomposition. The variability in the instantaneous firing rate was assessed at two or more levels of contraction in each muscle. Results: We found each muscle tested had a homogeneous population. There were no tonic and kinetic motor units. But there were differences in the variability in the instantaneous firing rate in the 4 muscles tested. Conclusion: Motor unit firing behavior in a muscle may be fitted for its function. Copyright (C) 2000 Elsevier Science Ireland Ltd.

Original languageEnglish
Pages (from-to)2196-2199
Number of pages4
JournalClinical Neurophysiology
Issue number12
Publication statusPublished - 2000 Nov 21



  • Decomposition technique
  • Kinetic
  • Mean inter-spike interval
  • Motor unit
  • Tonic
  • Variability

ASJC Scopus subject areas

  • Sensory Systems
  • Neurology
  • Clinical Neurology
  • Physiology (medical)

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