Skip to main content
NCBI home page
The Journal of Physiology logoLink to The Journal of Physiology
. 1982;329:113–128. doi: 10.1113/jphysiol.1982.sp014293

Behaviour of human motor units in different muscles during linearly varying contractions

C J de Luca 1,2, R S LeFever 1,2, M P McCue 1,2, A P Xenakis 1,2,*
PMCID: PMC1224770  PMID: 7143246

Abstract

1. The electrical activity of up to eight concurrently active motor units has been recorded from the human deltoid and first dorsal interosseous (f.d.i.) muscles. The detected myoelectric signals have been decomposed into their constituent motor-unit action potential trains using a recently developed technique.

2. Concurrently active motor unit behaviour has been examined during triangular force-varying isometric contractions reaching 40 and 80% of maximal voluntary contraction (m.v.c.). Experiments were performed on four normal subjects and three groups of highly trained performers (long-distance swimmers, powerlifters and pianists).

3. Results revealed a highly ordered recruitment and decruitment scheme, based on motoneurone excitability, in both muscles and in all subject groups.

4. Differences were observed between the initial (recruitment) and final (decruitment) firing rates in each muscle. These parameters were invariant with respect to the force rates studied, although some differences were observed among subject groups.

5. In general, firing rates of f.d.i. motor units increased steadily with increasing force (up to 80% m.v.c.). The firing rates of deltoid motor units rose sharply just after recruitment and then increased only slightly thereafter.

6. Recruitment was found to be the major mechanism for generating extra force between 40 and 80% m.v.c. in the deltoid, while rate coding played the major role in the f.d.i.

7. The potential of rate coding for increasing force levels up to m.v.c. is discussed.

Full text

PDF
113

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Baldissera F., Gustafsson B., Parmiggiani F. Saturating summation of the afterhyperpolarization conductance in spinal motoneurones: a mechanism for 'secondary range' repetitive firing. Brain Res. 1978 May 5;146(1):69–82. doi: 10.1016/0006-8993(78)90218-4. [DOI] [PubMed] [Google Scholar]
  2. Clamann H. P. Activity of single motor units during isometric tension. Neurology. 1970 Mar;20(3):254–260. doi: 10.1212/wnl.20.3.254. [DOI] [PubMed] [Google Scholar]
  3. De Luca C. J., Forrest W. J. Some properties of motor unit action potential trains recorded during constant force isometric contractions in man. Kybernetik. 1973 Mar;12(3):160–168. doi: 10.1007/BF00289169. [DOI] [PubMed] [Google Scholar]
  4. De Luca C. J., LeFever R. S., McCue M. P., Xenakis A. P. Control scheme governing concurrently active human motor units during voluntary contractions. J Physiol. 1982 Aug;329:129–142. doi: 10.1113/jphysiol.1982.sp014294. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. De Luca C. J. Physiology and mathematics of myoelectric signals. IEEE Trans Biomed Eng. 1979 Jun;26(6):313–325. doi: 10.1109/tbme.1979.326534. [DOI] [PubMed] [Google Scholar]
  6. Desmedt J. E., Godaux E. Ballistic contractions in man: characteristic recruitment pattern of single motor units of the tibialis anterior muscle. J Physiol. 1977 Jan;264(3):673–693. doi: 10.1113/jphysiol.1977.sp011689. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. FEINSTEIN B., LINDEGARD B., NYMAN E., WOHLFART G. Morphologic studies of motor units in normal human muscles. Acta Anat (Basel) 1955;23(2):127–142. doi: 10.1159/000140989. [DOI] [PubMed] [Google Scholar]
  8. Freund H. J., Büdingen H. J., Dietz V. Activity of single motor units from human forearm muscles during voluntary isometric contractions. J Neurophysiol. 1975 Jul;38(4):933–946. doi: 10.1152/jn.1975.38.4.933. [DOI] [PubMed] [Google Scholar]
  9. GRANIT R., PHILLIPS C. G., SKOGLUND S., STEG G. Differentiation of tonic from phasic alpha ventral horn cells by stretch, pinna and crossed extensor reflexes. J Neurophysiol. 1957 Sep;20(5):470–481. doi: 10.1152/jn.1957.20.5.470. [DOI] [PubMed] [Google Scholar]
  10. Gollnick P. D., Armstrong R. B., Saltin B., Saubert C. W., 4th, Sembrowich W. L., Shepherd R. E. Effect of training on enzyme activity and fiber composition of human skeletal muscle. J Appl Physiol. 1973 Jan;34(1):107–111. doi: 10.1152/jappl.1973.34.1.107. [DOI] [PubMed] [Google Scholar]
  11. HENNEMAN E., SOMJEN G., CARPENTER D. O. FUNCTIONAL SIGNIFICANCE OF CELL SIZE IN SPINAL MOTONEURONS. J Neurophysiol. 1965 May;28:560–580. doi: 10.1152/jn.1965.28.3.560. [DOI] [PubMed] [Google Scholar]
  12. Hannerz J. Discharge properties of motor units in relation to recruitment order in voluntary contraction. Acta Physiol Scand. 1974 Jul;91(3):374–385. doi: 10.1111/j.1748-1716.1974.tb05692.x. [DOI] [PubMed] [Google Scholar]
  13. Harris D. A., Henneman E. Different species of alpha motoneurons in same pool: further evidence from effects of inhibition on their firing rates. J Neurophysiol. 1979 Jul;42(4):927–935. doi: 10.1152/jn.1979.42.4.927. [DOI] [PubMed] [Google Scholar]
  14. Harris D. A., Henneman E. Identification of two species of alpha motoneurons in cat's plantaris pool. J Neurophysiol. 1977 Jan;40(1):16–25. doi: 10.1152/jn.1977.40.1.16. [DOI] [PubMed] [Google Scholar]
  15. Johnson M. A., Polgar J., Weightman D., Appleton D. Data on the distribution of fibre types in thirty-six human muscles. An autopsy study. J Neurol Sci. 1973 Jan;18(1):111–129. doi: 10.1016/0022-510x(73)90023-3. [DOI] [PubMed] [Google Scholar]
  16. Kanosue K., Yoshida M., Akazawa K., Fujii K. The number of active motor units and their firing rates in voluntary contraction of human brachialis muscle. Jpn J Physiol. 1979;29(4):427–443. doi: 10.2170/jjphysiol.29.427. [DOI] [PubMed] [Google Scholar]
  17. Kosarov D., Gydikov A. Dependence of the discharge frequency of motor units in different human muscles upon the level of the isometric muscle tension. Electromyogr Clin Neurophysiol. 1976 Aug-Sep;16(4):293–306. [PubMed] [Google Scholar]
  18. LeFever R. S., De Luca C. J. A procedure for decomposing the myoelectric signal into its constituent action potentials--Part I: Technique, theory, and implementation. IEEE Trans Biomed Eng. 1982 Mar;29(3):149–157. doi: 10.1109/tbme.1982.324881. [DOI] [PubMed] [Google Scholar]
  19. LeFever R. S., Xenakis A. P., De Luca C. J. A procedure for decomposing the myoelectric signal into its constituent action potentials--Part II: Execution and test for accuracy. IEEE Trans Biomed Eng. 1982 Mar;29(3):158–164. doi: 10.1109/TBME.1982.324882. [DOI] [PubMed] [Google Scholar]
  20. MCPHEDRAN A. M., WUERKER R. B., HENNEMAN E. PROPERTIES OF MOTOR UNITS IN A HETEROGENEOUS PALE MUSCLE (M. GASTROCNEMIUS) OF THE CAT. J Neurophysiol. 1965 Jan;28:85–99. doi: 10.1152/jn.1965.28.1.85. [DOI] [PubMed] [Google Scholar]
  21. Milner-Brown H. S., Stein R. B., Yemm R. Changes in firing rate of human motor units during linearly changing voluntary contractions. J Physiol. 1973 Apr;230(2):371–390. doi: 10.1113/jphysiol.1973.sp010193. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. Milner-Brown H. S., Stein R. B., Yemm R. The orderly recruitment of human motor units during voluntary isometric contractions. J Physiol. 1973 Apr;230(2):359–370. doi: 10.1113/jphysiol.1973.sp010192. [DOI] [PMC free article] [PubMed] [Google Scholar]
  23. Olson C. B., Swett C. P., Jr Effect of prior activity on properties of different types of motor units. J Neurophysiol. 1971 Jan;34(1):1–16. doi: 10.1152/jn.1971.34.1.1. [DOI] [PubMed] [Google Scholar]
  24. Person R. S., Kudina L. P. Discharge frequency and discharge pattern of human motor units during voluntary contraction of muscle. Electroencephalogr Clin Neurophysiol. 1972 May;32(5):471–483. doi: 10.1016/0013-4694(72)90058-2. [DOI] [PubMed] [Google Scholar]
  25. Salmons S., Henriksson J. The adaptive response of skeletal muscle to increased use. Muscle Nerve. 1981 Mar-Apr;4(2):94–105. doi: 10.1002/mus.880040204. [DOI] [PubMed] [Google Scholar]
  26. Shiavi R., Negin M. The effect of measurement errors on correlation estimates in spike-interval sequences. IEEE Trans Biomed Eng. 1973 Sep;20(5):374–378. [PubMed] [Google Scholar]
  27. Stephens J. A., Taylor A. Fatigue of maintained voluntary muscle contraction in man. J Physiol. 1972 Jan;220(1):1–18. doi: 10.1113/jphysiol.1972.sp009691. [DOI] [PMC free article] [PubMed] [Google Scholar]
  28. Tanji J., Kato M. Firing rate of individual motor units in voluntary contraction of abductor digiti minimi muscle in man. Exp Neurol. 1973 Sep;40(3):771–783. doi: 10.1016/0014-4886(73)90111-8. [DOI] [PubMed] [Google Scholar]
  29. Warmolts J. R., Engel W. K. Open-biopsy electromyography. I. Correlation of motor unit behavior with histochemical muscle fiber type in human limb muscle. Arch Neurol. 1972 Dec;27(6):512–517. doi: 10.1001/archneur.1972.00490180048011. [DOI] [PubMed] [Google Scholar]

Articles from The Journal of Physiology are provided here courtesy of The Physiological Society

RESOURCES