Fatigue pp 161-171 | Cite as

Human Motor Units Studied by Intramuscular Microstimulation

  • J. M. Elek
  • R. Dengler
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 384)


We recorded twitch parameters of motor units of the human first dorsal interosseus muscle applying low-rate intramuscular microstimulation of motor axons (IMS) or spike-triggered averaging (STA). The values of contraction time, half-relaxation time and maximal rate of rise of force were significantly smaller in the STA studies. The reduction corresponded to the effect expected from partial twitch fusion. Twitch amplitudes, however, were not smaller than those in the IMS studies, indicating that other factors, such as motor unit synchronization, compensate for the effects of partial fusion.


Amyotrophic Lateral Sclerosis Motor Unit Maximal Voluntary Contraction Spinal Muscular Atrophy Contraction Time 
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  1. Andreassen S & Bar-On E (1983). Estimation of motor unit twitches. IEEE Transactions of Biomedical Engineering 30, 742–748.CrossRefGoogle Scholar
  2. Calancie B & Bawa P (1986). Limitations of the spike-triggered averaging technique. Muscle & Nerve 9, 78–83.CrossRefGoogle Scholar
  3. Clamann HP & Schelhorn TB (1988). Nonlinear force addition of newly recruited motor units in the cat hindlimb. Muscle & Nerve 11, 1079–1089.CrossRefGoogle Scholar
  4. Dengler R, Konstanzer A, Küther G, Hesse S, Wolf W & Struppler A (1990). Amyotrophic lateral sclerosis: macro-EMG and twitch forces of single motor units. Muscle & Nerve 13, 545–550.CrossRefGoogle Scholar
  5. Dengler R, Kossev A, Wohlfarth K, Schubert M, Elek J & Wolf W (1992). F-waves and motor unit size. Muscle & Nerve 15, 1138–1142.CrossRefGoogle Scholar
  6. Dengler R, Wolf W, Birk P & Struppler A (1984). Synchronous discharges in pairs of steadily firing motor units tend to form clusters. Neuroscience Letters 47, 167–172.PubMedCrossRefGoogle Scholar
  7. Elek JM, Kossev A, Dengler R, Schubert M, Wohlfarth K & Wolf W (1992). Parameters of human motor unit twitches obtained by intramuscular microstimulation. Neuromuscular Disorders 2, 261–267.PubMedCrossRefGoogle Scholar
  8. McPhedran AM, Wuerker RB & Hennemann E (1965). Properties of motor units in a homogeneous red muscle (m. soleus) of the cat. Journal of Neurophysiology 28, 71–84.PubMedGoogle Scholar
  9. Milner-Brown HS, Stein RB & Yemm R (1973a). The contractile properties of human motor units during voluntary isometric contractions. Journal of Physiology (London) 228, 285–306.Google Scholar
  10. Milner-Brown HS, Stein RB & Yemm R (1973b). The orderly recruitment of human motor units during voluntary isometric contractions. Journal of Physiology (London) 230, 359–370.Google Scholar
  11. Monster AW & Chan H (1977). Isometric force production by motor units of extensor digitorum communis muscle in man. Journal of Neurophysiology 40, 1432–1443.PubMedGoogle Scholar
  12. Nordstrom MA & Miles TS (1990). Fatigue of single motor units in human masseter muscle. Journal of Applied Physiology 68, 26–34.PubMedGoogle Scholar
  13. Nordstrom MA, Miles T & Veale J (1989). Effect of motor unit firing pattern on twitches obtained by spike-triggered averaging. Muscle & Nerve 12, 556–567.CrossRefGoogle Scholar
  14. Sears TA & Stagg D (1976). Short-term synchronization of intercostal motoneurone activity. Journal of Physiology (London) 263, 357–381.Google Scholar
  15. Stalberg E & Fawcett PRW (1982). Macro-EMG in healthy subjects of different ages. Journal of Neurology, Neurosurgery & Psychiatry 45, 870–878.CrossRefGoogle Scholar
  16. Stein RB, French AS, Mannard A & Yemm R (1972). New methods for analysing motor function in man and animals. Brain Research 49, 187–192.CrossRefGoogle Scholar
  17. Stein RB & Yang JF (1990). Methods for estimating the number of motor units in human muscles. Annals of Neurology 28, 487–495.PubMedCrossRefGoogle Scholar
  18. Stephens JA & Usherwood TP (1977). The mechanical properties of human motor units with special reference to their fatiguability and recruitment threshold. Brain Research 125, 91–97.PubMedCrossRefGoogle Scholar
  19. Taylor A & Stephens JA (1976). Study of human motor unit contractions by controlled intramuscular microstimulation. Brain Research 117, 331–335.PubMedCrossRefGoogle Scholar
  20. Thomas CK, Bigland-Ritchie B, Westling G & Johansson RS (1990a). A comparison of human thenar motor-unit properties studied by intraneural motor-axon stimulation and spike-triggered averaging. Journal of Neurophysiology 64, 1347–1351.PubMedGoogle Scholar
  21. Thomas CK, Johansson RS, Westling G & Bigland-Ritchie B (1990b). Twitch properties of human thenar motor units measured in response to intraneural motor-axon stimulation. Journal of Neurophysiology 64, 1339–1346.PubMedGoogle Scholar
  22. Yang JF, Stein RB, Jhamandas J & Gordon T (1990). Motor unit numbers and contractile properties after spinal cord injury. Annals of Neurology 28, 496–502.PubMedCrossRefGoogle Scholar
  23. Young YL & Mayer RF (1982). Physiological alterations of motor units in hemiplegia. Journal of Neurological Sciences 54, 401–412.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media New York 1995

Authors and Affiliations

  • J. M. Elek
    • 1
  • R. Dengler
    • 1
  1. 1.Department of Neurology and Clinical NeurophysiologyMedical School of HannoverHannoverGermany

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