A single 20-gram oral dose of whey peptide increases phosphorylation of mTOR at Ser2448 and S6K1 at Thr389 in skeletal muscle of healthy young adults within one hour, and the magnitude of S6K1 phosphorylation is positively correlated with the dose per kilogram of body weight (r²=0.7128, p<0.05).

When whey peptide is swallowed, it breaks down into amino acids that enter the bloodstream and move into muscle cells. These amino acids, especially leucine, bind to sensors inside the muscle that turn on a molecular switch called mTORC1. Once activated, mTORC1 adds a phosphate group to itself at a specific spot and then passes the signal to another protein, S6K1, which also gets phosphorylated. The more whey peptide consumed per kilogram of body weight, the stronger this signal becomes.