Essential amino acids, also called indispensable amino acids, are not synthesized in the body in humans and must be supplied in the diet either as free amino acids or as constituents of dietary proteins. By this criterion, the eight amino acids essential in man are:

. Isoleucine*

. Leucine*

. Lysine

. Methionine

. Phenylalanine

. Threonine

. Tryptophan

. Valine*

The use of amino acids in and around training and at other times, especially the essential amino acids, has been shown to acutely increase muscle protein synthesis.1,2 The question in many people’s minds, however, is whether the body compensates for this acute increase after training by decreasing protein synthesis later on during the day or even at night. In other words, does the increase in protein synthesis in response to amino acid ingestion that is seen after training result in a long-term anabolic response, one that is above what we would normally see without their use after training.