Fatiguing contractions of tongue protrudor and retractor muscles: Influence of systemic hypoxia

David D. Fuller, Ralph F. Fregosi

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


The influence of systemic hypoxia on the endurance performance of tongue protrudor and retractor muscles was examined in anesthetized, ventilated rats. Tongue protrudor (genioglossus) or retractor (hyoglossus and styloglossus) muscles were activated via medial or lateral XII nerve branch stimulation (0.1-ms pulse; 40 Hz; 330-ms trains; 1 train/s). Maximal evoked potentials (M waves) of genioglossus and hyoglossus were monitored with electromyography. Fatigue tests were performed under normoxic and hypoxic (arterial PO2 = 50 ± 1 Torr) conditions in separate animals. The fatigue index (FI; %initial force) after 5 min of normoxic stimulation was 85 ± 6 and 79 ± 7% for tongue protrudor and retractor muscles, respectively; these values were significantly lower during hypoxia (protrudor FI = 52 ± 10, retractor FI = 18 ± 6%; P < 0.05). Protrudor and retractor muscle M-wave amplitude declined over the course of the hypoxic fatigue test but did not change during normoxia (P < 0.05). We conclude that hypoxia attenuates tongue protrudor and retractor muscle endurance performance; potential mechanisms include neuromuscular transmission failure and/or diminished sarcolemmal excitability.

Original languageEnglish (US)
Pages (from-to)2123-2130
Number of pages8
JournalJournal of Applied Physiology
Issue number6
StatePublished - 2000


  • Fatigue
  • Genioglossus
  • Hyoglossus
  • M wave
  • Stylogossus

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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