Key benefits Metabolite of the BCAA leucine Supports muscle growth and maintenance 1.5g HMB per serving  240mg calcium per serving Convenient tablets Product overview HMB (Beta-Hydroxy Beta-Methylbutyrate) is a substance naturally formed within the body when breaking down leucine. This branched-chain amino acid is one of the essential building blocks of protein, which promotes lean muscle growth and maintenance. A popular supplement in the weightlifting community, HMB is a great choice when upping the intensity of your workouts. Plus, these convenient capsules also offer a boost of calcium – a mineral needed to support muscle function.