HMB (calcium beta-hydroxy-beta-methylbutyrate) is produced in the body during the metabolism of the essential amino acid leucine.
HMB helps increase muscle protein through two important mechanisms, increasing protein synthesis and decreasing protein breakdown. The balance between protein synthesis and protein breakdown determines if you are building or breaking down muscle. This is where HMB plays a key role, as HMB tips the scale in favor of building muscle.
HMB stimulates protein synthesis in muscle through multiple mechanisms, including the mTOR/p70S6K pathway, which stimulates translation initiation of protein synthesis. (Many of these effects are shared with leucine; however, studies have shown HMB is more potent than leucine in promoting gains.)
HMB decreases protein breakdown at a molecular level caused by training. HMB results in decreasing the key regulating components of the ubiquitin-proteasome proteolytic pathway, which results in less muscle loss and damage.
Therefore, the increase in synthesis and decrease in breakdown results in a faster recovery after exercise and greater gains of muscle mass.
Research has also shown HMB increases VO2max, respiratory compensation point and the time to the onset of blood lactate accumulation, which allows athletes to tolerate high-intensity activity over a longer period of time.
Learn more at HMB.org