The antioxidant N-acetylcysteine (NAC) has been demonstrated to reduce muscle contractile fatigue in a laboratory setting (Reid et al., 1994). This investigation aimed to examine the ergogenic effect of short-term oral NAC supplementation and associated changes in red-ox balance and inflammation during intense training. Methods A double blind, randomised placebo-controlled crossover design was used to assess 9 d oral NAC supplementation (1200 mg/day) in 8 well-trained triathletes (age 23.6 ± 3.2 yrs,VO2peak 63.3 ± 4.8 ml/kg/min). For each supplement trial (NAC and placebo), baseline venous blood and urine samples were taken and a presupplementation cycle ergometer race simulation was performed. Following the loading period, further samples were collected preexercise, post-exercise, 2 h and 24 h following the post-supplementation cycle ergometer race simulation which consisted of sprint and time trial efforts. Changes in plasma total antioxidant capacity (TAC), ferric reducing ability of plasma (FRAP), thiobarbituric acid-reactive substances (TBARS), interlukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1) were assessed. Nuclear factor- kB (NF-kB) in peripheral mononuclear cells extracts and urinary 15-isoprostane F2t concentration (F2Isoprostanes) were measured at the same time points. Training load was matched for each trial and the Daily Analysis of Like Demands for Athletes (DALDA) was used to monitor well-being. The experimental procedure was repeated with the remaining supplement after a 3 week washout. Changes in biochemical and performance parameters were analysed using a factorial two-way analysis of variance. Results NAC improved sprint performance during the cycle ergometer race simulation (P<0.001), but not time trial performance. Supplementation with NAC augmented post-exercise plasma TAC (P=0.005), reduced exercise-induced oxidative damage, [plasma TBARS (P=0.002); urinary F2Isoprostanes (P=0.010)] and attenuated inflammation [plasma IL-6 (P=0.002); MCP-1 (P=0.012)]. NAC increased post-exercise NF-kB activity (P < 0.001). A greater number of `worse than normal` responses in the DALDA (P = 0.050) was reported in the placebo trial. Discussion Oral NAC supplementation improved cycling performance via an improved red-ox balance and promoted adaptive processes in well-trained athletes undergoing strenuous physical training. This finding supports the use of NAC as an ergogenic aid in a practical sporting setting. Moreover, in agreement with previous research, athletes displayed a greater ability to cope with intense physical training with antioxidant supplementation which did not interfere with physiological adaptive processes (Palazzetti et al., 2004).
© Copyright 2012 17th Annual Congress of the European College of Sport Science (ECSS), Bruges, 4. -7. July 2012. Veröffentlicht von Vrije Universiteit Brussel. Alle Rechte vorbehalten.