Effect of N-acetylcysteine on Cycling Performance after Intensified Training

SLATTERY, KATIE MAY1; DASCOMBE, BEN2; WALLACE, LEE KENNETH1; BENTLEY, DAVID J.3; COUTTS, AARON JAMES1

Medicine & Science in Sports & Exercise: June 2014 - Volume 46 - Issue 6 - p 1114–1123
doi: 10.1249/MSS.0000000000000222
Basic Sciences

Purpose: This investigation examined the ergogenic effect of short-term oral N-acetylcysteine (NAC) supplementation and the associated changes in redox balance and inflammation during intense training.

Methods: A double-blind randomized placebo-controlled crossover design was used to assess 9 d of oral NAC supplementation (1200 mg·d−1) in 10 well-trained triathletes. For each supplement trial (NAC and placebo), baseline venous blood and urine samples were taken, and a presupplementation cycle ergometer race simulation was performed. After the loading period, further samples were collected preexercise, postexercise, and 2 and 24 h after the postsupplementation cycle ergometer race simulation. Changes in total antioxidant capacity, ferric reducing ability of plasma, reduced glutathione, oxidized glutathione, thiobarbituric acid-reactive substances, interleukin 6, xanthine oxidase, hypoxanthine, monocyte chemotactic protein 1, nuclear factor κB, and urinary 15-isoprostane F2t concentration were assessed. The experimental procedure was repeated with the remaining supplement after a 3-wk washout. Eight participants completed both supplementation trials.

Results: NAC improved sprint performance during the cycle ergometer race simulation (P < 0.001, ηp2 = 0.03). Supplementation with NAC also augmented postexercise plasma total antioxidant capacity (P = 0.005, ηp2 = 0.19), reduced exercise-induced oxidative damage (plasma thiobarbituric acid-reactive substances, P = 0.002, ηp2 = 0.22; urinary 15-isoprostane F2t concentration, P = 0.010, ηp2 = 0.431), attenuated inflammation (plasma interleukin 6, P = 0.002, ηp2 = 0.22; monocyte chemotactic protein 1, P = 0.012, ηp2 = 0.17), and increased postexercise nuclear factor κB activity (P < 0.001, ηp2 = 0.21).

Conclusion: Oral NAC supplementation improved cycling performance via an improved redox balance and promoted adaptive processes in well-trained athletes undergoing strenuous physical training.

1Sport and Exercise Discipline Group, Faculty of Health, University of Technology, Sydney, AUSTRALIA; 2Applied Sports Science and Exercise Testing Laboratory, School of Environmental and Life Sciences, University of Newcastle, Callaghan, AUSTRALIA; and 3Human Exercise Performance Laboratory, School of Medical Science, University of Adelaide, Adelaide, AUSTRALIA

Address for correspondence: Katie Slattery, NSW Institute of Sport, PO Box 476, Sydney Olympic Park, NSW 2127, Australia; E-mail: katie.slattery@nswis.com.au.

Submitted for publication April 2013.

Accepted for publication October 2013.

© 2014 American College of Sports Medicine