Impulse propagation and muscle activation in long maximal voluntary contractions

C. K. Thomas, J. J. Woods, B. Bigland-Ritchie

Research output: Contribution to journalArticle

67 Scopus citations

Abstract

With fatigue, force generation may be limited by several factors, including impaired impulse transmission and/or reduced motor drive. In 5-min isometric maximal voluntary contractions, no decline was seen in the peak amplitude of the tibialis anterior compound muscle mass action potential (M wave) either during or immediately after the voluntary effort, provided maximal nerve stimulation was retained. For first dorsal interosseous (FDI) muscle, M wave amplitudes declined by 19.4 ± 1.6% during the first 2 min but did not change significantly thereafter, despite the continued force reduction (up to 94% in 5 min for both muscles). The duration of the FDI M waves increased (>30%), suggesting that the small decline in amplitude was the result of increased dispersion between the responses of different motor units. Some subjects kept FDI maximally activated throughout, but when they used tibialis anterior, twitch occlusion and tetanic muscle stimulation showed that most subjects were usually only able to do so for the first 60 s and thereafter only during brief 'extra efforts'. Thus force loss during isometric voluntary contractions sustained at the highest intensities results mainly from failure of processes within the muscle fibers.

Original languageEnglish (US)
Pages (from-to)1835-1842
Number of pages8
JournalJournal of applied physiology
Volume67
Issue number5
DOIs
StatePublished - Jan 1 1989

Keywords

  • central motor drive
  • Human muscle fatigue
  • neuromuscular transmission

ASJC Scopus subject areas

  • Endocrinology
  • Physiology
  • Orthopedics and Sports Medicine
  • Physical Therapy, Sports Therapy and Rehabilitation

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