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

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 all acute oral dose of NAC on RMF during heavy exercise. Subjects (n = 8) were given either placebo (PLA) or NAC (1800 mg) 45 min prior to a 30 min constant load (85V(O2peak)), discontinuous exercise test. Maximum respiratory pressures (inspiratory, Pl(max); expiratory, PEmax) and venous blood samples were made prior to and following each 5 min of exercise. There was no difference (p > 0.05) in Pl(max) between NAC(127.9 +/- 34.1 cmH(2)O)or PLA (134.1 +/- 28.1 cmH(2)O)at rest. During exercise, Pl(max) was significantly lower with PLA (similar to 14%) compared to NAC at 25 and 30 min Suggesting less RMF with NAC. There were no differences (p > 0.05) between groups in PEmax, V-O2, V-F, or heart rate at rest or throughout exercise. These results suggest that an acute dose of NAC reduces RMF during heavy exercise. (C) 2008 Elsevier B.V. All rights reserved.