Oral N‐acetylcysteine supplementation does not improve cycling time trial performance

Edwards, David G.; Hayman, Margaret; Roy, Matthew S.; Kenefick, Robert W.

doi:10.1096/fasebj.20.4.a811-c

Cited by 2 publications

(2 citation statements)

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“…Despite NAC acting to preserve gross efficiency during cycling, and possibly having an effect on performance during submaximal exercise, there appeared to be no effect of NAC supplementation on 1-km TT performance in WomenNC and WomenOC and thus, the data does not fully support our hypothesis. This null finding agrees with some studies conducted in men (Edwards et al 2006 ; Medved et al 2003 ), but not all, whereby several studies have found oral NAC supplementation to have ergogenic effects on performance (Cobley et al 2011 ; Paschalis et al 2018 ; Rhodes et al 2019 ; Slattery et al 2014 ), particularly in individuals with a glutathione deficiency (Paschalis et al 2018 ). NAC has been reported to improve repeat sprint cycling performance (Slattery et al 2014 ), performance of a repeated high-intensity intermittent shuttle (running) test (Cobley et al 2011 ), maximum shuttle (running) sprint time (Rhodes et al 2019 ) and cycling TT, Wingate and O 2 peak (Paschalis et al 2018 ).…”

Section: Nac and Performancesupporting

confidence: 87%

“…NAC has been reported to improve repeat sprint cycling performance (Slattery et al 2014 ), performance of a repeated high-intensity intermittent shuttle (running) test (Cobley et al 2011 ), maximum shuttle (running) sprint time (Rhodes et al 2019 ) and cycling TT, Wingate and O 2 peak (Paschalis et al 2018 ). Whereas, cycling TT performance (Edwards et al 2006 ; Trewin et al 2013 ), and high intensity cycling efforts (Medved et al 2003 ) were not influenced by NAC supplementation. Since NAC is reported to be more effective in individuals with a glutathione deficiency, the incongruent findings may be related to baseline glutathione concentrations in the study participants (Paschalis et al 2018 ).…”

Section: Nac and Performancementioning

confidence: 97%

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Blood oxidative stress biomarkers in women: influence of oral contraception, exercise, and N-acetylcysteine

et al. 2022

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Purpose To compare physiological responses to submaximal cycling and sprint cycling performance in women using oral contraceptives (WomenOC) and naturally cycling women (WomenNC) and to determine whether N-acetylcysteine (NAC) supplementation mediates these responses. Methods Twenty recreationally trained women completed five exercise trials (i.e., an incremental cycling test, a familiarisation trial, a baseline performance trial and two double-blind crossover intervention trials). During the intervention trials participants supplemented with NAC or a placebo 1 h before exercise. Cardiopulmonary parameters and blood biochemistry were assessed during 40 min of fixed-intensity cycling at 105% of gas-exchange threshold and after 1-km cycling time-trial. Results WomenOC had higher ventilation (β [95% CI] = 0.07 L·min−1 [0.01, 0.14]), malondialdehydes (β = 12.00 mmol·L−1 [6.82, 17.17]) and C-reactive protein (1.53 mg·L−1 [0.76, 2.30]), whereas glutathione peroxidase was lower (β = 22.62 mU·mL−1 [− 41.32, − 3.91]) compared to WomenNC during fixed-intensity cycling. Plasma thiols were higher at all timepoints after NAC ingestion compared to placebo, irrespective of group (all p < 0.001; d = 1.45 to 2.34). For WomenNC but not WomenOC, the exercise-induced increase in malondialdehyde observed in the placebo trial was blunted after NAC ingestion, with lower values at 40 min (p = 0.018; d = 0.73). NAC did not affect cycling time-trial performance. Conclusions Blood biomarkers relating to oxidative stress and inflammation are elevated in WomenOC during exercise. There may be an increased strain on the endogenous antioxidant system during exercise, since NAC supplementation in WomenOC did not dampen the exercise-induced increase in malondialdehyde. Future investigations should explore the impact of elevated oxidative stress on exercise adaptations or recovery from exercise in WomenOC.

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