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

Abstract

Objective: 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. The aim of this study was 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 8 wk. In the last 3 wk 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, whereas ALA and G+A supplementation reduced plasma LDH and creatine kinase 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, 8-isoprostane and GSH in plasma; adenosine monophosphate deaminase, citrate synthase and monocarboxylate transporters 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.

Keywords: Amino acids; Glycogen; Muscle damage; Oxidative stress; Peripheral fatigue; Physical exercise; l-alanyl-l-glutamine.