HMB, calcium β-hydroxy-β-methylbutyrate, is a molecule that comes solely from the degradation of an amino acid: leucine. Produced in small quantities by the body, HMB is used by people willing to increase their muscle mass during intensive training.
HMB prevents the breakdown of proteins and promotes an increase in their synthesis, thus allowing for muscle gain. Lean mass then increases and helps to build muscle strength. The capacities are thus improved as the training sessions progress.