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1 Muscle, Ions and Exercise Group; Centre for Rehabilitation, Exercise and Sport Science; School of Human Movement, Recreation and Performance, Victoria University of Technology, Melbourne, Victoria, Australia
2 Department of Anaesthesia, Austin and Repatriation Medical Centre, Melbourne, Victoria, Australia
3 Department of Anaesthesia and Pain Management, Royal Melbourne Hospital, Melbourne, Victoria, Australia
* To whom correspondence should be addressed. E-mail: michael.mckenna{at}vu.edu.au.
Infusion of the antioxidant N-acetylcysteine (NAC) reduces fatigability in electrically evoked human muscle contraction, but due to reported adverse reactions, no studies have investigated NAC infusion effects during voluntary exercise in humans. We investigated whether a modified NAC infusion protocol (125 mg.kg-1.hr-1 for 15 min, then 25 mg.kg-1.hr-1) altered blood redox status and enhanced performance during intense, intermittent exercise. Eight untrained males participated in a counterbalanced, double-blind, crossover study, receiving NAC or saline (CON) before and during cycling exercise, comprising three 45 s bouts and a fourth bout continued to fatigue, at 130%VO2peak. Arterialised venous blood was analyzed for glutathione status, hematology and plasma electrolytes. NAC infusion induced no severe adverse reactions. Exercise decreased the reduced glutathione (P<0.005) and increased oxidized glutathione concentrations (P<0.005); NAC attenuated both effects (P<0.05). NAC increased the rise in plasma [K+]/work ratio (P<0.05), indicating impaired K+ regulation; whilst time to fatigue was unchanged (NAC 102±45s, CON 107±53s). Thus, NAC infusion altered blood redox status during intense intermittent exercise, but did not attenuate fatigue.
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