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- Title
N-acetylcysteine alters substrate metabolism during high-intensity cycle exercise in well-trained humans.
- Authors
Trewin, Adam J.; Petersen, Aaron C.; Billaut, Francois; McQuade, Leon R.; McInerney, Bernie V.; Stepto, Nigel K.
- Abstract
We investigated the effects of N-acetylcysteine (NAC) on metabolism during fixed work rate high-intensity interval exercise (HIIE) and self-paced 10-min time-trial (TT10) performance. Nine well-trained male cyclists ( V̇O2peak, 69.4 ± 5.8 mL·kg−1·min−1; peak power output (PPO), 385 ± 43 W; mean ± SD) participated in a double-blind, repeated-measures, randomised crossover trial. Two trials (NAC supplementation and placebo) were performed 7 days apart consisting of 6 × 5 min HIIE bouts at 82% PPO (316 ± 40 W) separated by 1 min at 100 W, and then after 2 min of recovery at 100 W, TT10 was performed. Expired gases, venous blood, and electromyographic (EMG) data were collected. NAC did not influence blood glutathione but decreased lipid peroxidation compared with the placebo ( P < 0.05). Fat oxidation was elevated with NAC compared with the placebo during HIIE bouts 5 and 6 (9.9 ± 8.9 vs. 3.9 ± 4.8 μmol·kg−1·min−1; P < 0.05), as was blood glucose throughout HIIE (4.3 ± 0.6 vs. 3.8 ± 0.6 mmol·L−1; P < 0.05). Blood lactate was lower with NAC after TT10 (3.3 ± 1.3 vs. 4.2 ± 1.3 mmol·L−1; P < 0.05). Median EMG frequency of the vastus lateralis was lower with NAC during HIIE (79 ± 10 vs. 85 ± 10 Hz; P < 0.05), but not TT10 (82 ± 11 Hz). Finally, NAC decreased mean power output 4.9% ± 6.6% (effect size = -0.3 ± 0.4, mean ± 90% CI) during TT10 (305 ± 57 W vs. 319 ± 45 W). These data suggest that NAC alters substrate metabolism and muscle fibre type recruitment during HIIE, which is detrimental to time-trial performance.
- Subjects
BLOOD testing; REACTIVE oxygen species; ANALYSIS of variance; CONFIDENCE intervals; CROSSOVER trials; CYCLING; DIETARY supplements; ELECTROMYOGRAPHY; EXERCISE physiology; EXERCISE tests; STATISTICS; DATA analysis; TASK performance; EFFECT sizes (Statistics); RANDOMIZED controlled trials; REPEATED measures design; OXYGEN consumption; BLIND experiment; DATA analysis software; ACETYLCYSTEINE; DESCRIPTIVE statistics
- Publication
Applied Physiology, Nutrition & Metabolism, 2013, Vol 38, Issue 12, p1217
- ISSN
1715-5312
- Publication type
Article
- DOI
10.1139/apnm-2012-0482