Protein requirements in individuals who participate in endurance-based exercise training have
been suggested to be greater than the current recommended dietary allowance (RDA).
The biological value of protein depends on its amino acid composition. Essential amino acids
are believed to have main role on whole body protein metabolism. However, it remains to be
determined what role non-essential amino acids (NEAA) may have in regulating protein
metabolism and contributing to the increased protein requirements after endurance exercise.
The indicator amino acid oxidation (IAAO) method has clarified the individual amino acid
requirement in children, normal healthy adult and clinical populations. However, the IAAO
method has never been utilized for assessing the effect of NEAA on protein requirements after
The objective of the current study is to investigate the importance of NEAA for
endurance-trained male subjects.