Although several kinds of amino acids (AAs) are known to affect physiological actions during exercise, little is known about the combined effects of a mixture of several AAs on fatigue during exercise. The aim of the present study was to investigate the effect of an AA mixture supplement containing arginine, valine, and serine on exercise-induced fatigue in healthy volunteers. These AAs were selected because they were expected to reduce fatigue during exercise by acting the positive effects synergistically. A randomized, double-blinded, placebo-controlled crossover trial was conducted. Thirty-nine males ingested an AA mixture containing 3600 mg of arginine, 2200 mg of valine, and 200 mg of serine or a placebo each day for 14 days. On the 14th day, the participants completed an exercise trial on a cycle ergometer at 50% of VO2max for 120 min. After the two-week washout period, the participants repeated the same trial with the other test sample. The participant's feeling of fatigue based on a visual analog scale (VAS) and a rating of perceived exertion (RPE), as well as blood and physical parameters were evaluated. The feeling of fatigue based on VAS and RPE were significantly improved in AA compared to those in placebo. In the blood analysis, the increase in serum total ketone bodies during exercise and plasma tryptophan/branched-chain amino acids were significantly lower in AA than those in placebo. The present study demonstrated that supplementation with an AA mixture containing arginine, valine, and serine reduced the feeling of fatigue during exercise. The AA mixture also changed several blood parameters, which may contribute to the anti-fatigue effect.
Keywords: amino acid mixture; exercise; fatigue; visual analog scale.