Conventional amino acid compositions are primarily intendedto improve athletic performance or to promote fat-burning. Providedis an anti-fatigue agent which can prevent both of muscle fatigueand nerve strain concurrently. An anti-fatigue agent which comprisesan amino acid composition composed of specific amino acids inspecified amounts can prevent both of muscle fatigue and nerve strainconcurrently. As for the types and the ratio of the amounts of theamino acids contained in the amino acid composition, the amino acidcomposition preferably contains 30 to 200 parts by weight of proline,60 to 140 parts by weight of glycine, 50 to 260 parts by weightof alanine, 50 to 130 parts by weight of lysine, 30 to 75 partsby weight of tryptophan and 20 tb 40 parts by weight of histidine,more preferably further comprises 3 to 75 parts by weight of tyrosineand 15 to 45 parts by weight of arginine, still more preferablyfurther contains 30 to 55 parts by weight of valine, 35 to 60 partsby weight of leucine and 25 to 60 parts by weight of isoleucine.
