Beta-hydroxy-beta-methylbutyrate (HMB), a derivative of the essential amino acid leucine, is recognized for its anti-catabolic effect on skeletal muscle (Pinheiro 2012). HMB supplementation may provide several ergogenic benefits, including increased strength, power, and lean body mass, decreased fat mass, better recovery, and improvements in aerobic and anaerobic performance (Albert 2015). It may also play a role in muscle protein synthesis and along with the anti-catabolic effects, may serve to enhance muscle mass and strength in athletes. (Zanchi 2011)
A proposed mechanism of HMB supplementation for increasing strength and fat free mass is stimulation of the mTOR signaling pathway that leads to muscle protein synthesis. HMB may also have positive effects on several catabolic conditions. These include lessening the rise in catabolic biomarkers and stress hormones and mitigating decreases in power in athletes during periods of high-intensity training, high-density competitions, and first stages of injury recovery. (Albert 2015)
There is some evidence that the dietary supplement HMB can decrease muscle protein breakdown during the stress of exercise (Zanchi 2011). In general, HMB supplementation has demonstrated insignificant effects on fat free mass and strength in trained and competitive athletes. Also, the effects on muscle damage and recovery remain unclear. HMB may have some biological effect on muscular adaptations to exercise, but it does not appear to be a powerful ergogenic aid. Supplementing HMB may prove more useful for injury and rehabilitation to preserve muscle mass during periods of inactivity. (Rawson 2018)
The recommended dosing for HMB supplementation of 3g/day as an ergogenic aid appears to be well tolerated and safe. However, due to inconclusive data regarding athletic performance enhancement in humans, HMB cannot be widely recommended to athletes. This is because its effects may not prove to be more beneficial than just following the recommended protein intake requirements. There is emerging evidence that HMB in combination with creatine is a promising strategy to increase lean mass and strength, but future studies are needed to examine the effects of this combination in athletes. (Zanchi 2011, Rawson 2018)
Albert FJ, Morente-Sánchez J, Ortega FB, Castillo MJ, Gutiérrez, Á (2015). usefulness of β-hydroxy-β-methylbutyrate (hmb) supplementation in different sports: An update and practical implications. Nutricion Hospitalaria, 32(1), 20.
Pinheiro CH, Gerlinger-Romero F, Guimarães-Ferreira L, de Souza AL Jr, Vitzel KF, Nachbar RT, Nunes MT, Curi R (2012). Metabolic and functional effects of beta-hydroxy-beta-methylbutyrate (HMB) supplementation in skeletal muscle. European Journal of Applied Physiology, 112(7), 2531-2537.
Rawson ES, Miles MP, Larson-Meyer DE (2018). Dietary supplements for health, adaptation, and recovery in athletes. International Journal of Sport Nutrition and Exercise Metabolism, 28(2), 188-199.
Zanchi NE, Gerlinger-Romero F, Guimarães-Ferreira L, de Siqueira Filho MA, Felitti V, Lira FS, Seelaender M, Lancha AH Jr (2011). HMB supplementation: Clinical and athletic performance-related effects and mechanisms of action. Amino Acids, 40(4), 1015-1025.