The Number of Active Motor Units and Their Firing Rates in Voluntary Contraction of Human Brachialis Muscle

Kazuyuki Kanosue, Masaki Yoshida, Kenzo Akazawa, Katsuhuiko Fujii

研究成果: Article

81 被引用数 (Scopus)

抄録

To make clear the control mechanism of force generation in human muscle, the electrical activity of the brachialis muscle was studied at various levels of contraction force by recording single motor unit discharges as well as mass electromyograms (EMGs). The firing rate of motor units increased with force along an S-shaped curve. At low levels of force, motor units increased their firing rates steeply with force. At intermediate levels of force, each motor unit increased its firing rate linearly with force at lower rates. As the maximum of force was approached, the firing rate increased very steeply, reaching as high as 50 Hz or more. By applying a new method of statistical processing to mass EMGs, the number of active motor units and the size of action potential were estimated at each level of force. The number of active motor units increased monotonously with muscle force. Motor units recruited at high levels of force had larger amplitudes of action potentials than those recruited at lower levels. Calculations were made to determine how the relative contribution to an increase in muscle force is varied between recruitment and the increase in firing rate. The contribution of recruitment gradually decreased with the increase in force. Up to about 70% of the mixmum force, recruitment is the major mechanism for increasing the force of contraction.

本文言語English
ページ(範囲)427-443
ページ数17
ジャーナルJapanese Journal of Physiology
29
4
DOI
出版ステータスPublished - 1979

ASJC Scopus subject areas

  • Physiology

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