Effects of glutamine and alanine supplementation on muscle fatigue parameters of rats submitted to resistance training

Abstract Background Although glutamine and alanine have properties that could delay fatigue, recent evidence showed that these amino acids impaired central fatigue markers; nevertheless, the effect of this intervention on muscle fatigue is unknown. Objective This study aimed to investigate the effects of glutamine and alanine supplementation on muscle fatigue parameters in rats submitted to resistance training (RT). Methods Wistar rats were distributed into the following groups: sedentary (SED), exercised (CON), exercised and supplemented with alanine (ALA), glutamine and alanine in their free form (G+A) or L-alanyl-L-glutamine (DIP). Trained groups underwent a ladder-climbing exercise for eight weeks. In the last three weeks of RT, supplementations were offered in water with a 4% concentration. Results G+A and DIP supplementation increased the muscle content of glutamine and glutamate. DIP administration increased glycogen and lactate dehydrogenase (LDH) concentrations in muscle, while ALA and G+A supplementation reduced plasma LDH and creatine kinase (CK) levels. All trained groups presented higher levels of muscle glutathione (GSH) than SED. There was no difference between groups in lactate, xanthine, hypoxanthine, thiobarbituric acid reactive substances (TBARS), 8-isoprostane and GSH in plasma; adenosine monophosphate deaminase (AMPD), citrate synthase (CS) and monocarboxylate transporters (MCT-1 and -4) in muscle; and glycogen and GSH in the liver. Moreover, physical performance did not differ between groups. Conclusion Glutamine and alanine supplementation improved muscle fatigue markers without affecting exercise performance.