The most prevalent amino acid, glutamine, is present in high concentrations in your muscles.
In actuality, glutamine makes up around 60% of all the amino acids found in muscle. Although glutamine is categorized as a non-essential amino acid, because it gives your muscles fuel, there are times when your body needs more of it than it can make.
For instance, the body's glutamine levels are depleted during vigorous exercise because the body is under stress and the body's muscles and tendons need more of this amino acid.
In this situation, glutamine must be consumed from either food or supplements to reduce the loss of muscle.