Effects of N-acetylcysteine on respiratory muscle fatigue during heavy exercise

Respir Physiol Neurobiol. 2009 Jan 1;165(1):67-72. doi: 10.1016/j.resp.2008.10.008. Epub 2008 Oct 17.


Respiratory muscle fatigue (RMF) occurs during heavy exercise in humans. N-acetylcysteine (NAC) infusion has been shown to reduce RMF, suggesting that oxidative stress is a contributing factor. The purpose of the present study was to determine the effect of an acute oral dose of NAC on RMF during heavy exercise. Subjects (n=8) were given either placebo (PLA) or NAC (1,800 mg) 45 min prior to a 30 min constant load (85V(O)(2peak)), discontinuous exercise test. Maximum respiratory pressures (inspiratory, PI(max); expiratory, PE(max)) and venous blood samples were made prior to and following each 5 min of exercise. There was no difference (p>0.05) in PI(max) between NAC (127.9+/-34.1 cm H(2)O) or PLA (134.1+/-28.1cm H(2)O) at rest. During exercise, PI(max) was significantly lower with PLA ( approximately 14%) compared to NAC at 25 and 30 min suggesting less RMF with NAC. There were no differences (p>0.05) between groups in PE(max), V(O)(2), V(E), or heart rate at rest or throughout exercise. These results suggest that an acute dose of NAC reduces RMF during heavy exercise.

Publication types

  • Clinical Trial
  • Randomized Controlled Trial

MeSH terms

  • Acetylcysteine / pharmacology*
  • Adult
  • Analysis of Variance
  • Cross-Over Studies
  • Double-Blind Method
  • Exercise / physiology*
  • Free Radical Scavengers / pharmacology*
  • Glutathione / blood
  • Humans
  • Male
  • Muscle Fatigue / drug effects*
  • Muscle Fatigue / physiology
  • Oxygen Consumption / drug effects
  • Oxygen Consumption / physiology
  • Physical Endurance / drug effects
  • Physical Endurance / physiology
  • Respiration / drug effects
  • Respiratory Function Tests / methods
  • Respiratory Muscles / drug effects*
  • Young Adult


  • Free Radical Scavengers
  • Glutathione
  • Acetylcysteine