HMB stands for a complicated compound - beta-hydroxy-beta-methylbutyrate. It is not clear whether it is a derivative of vitamin or whether it should be classified in the group of short-chain fatty acids, but certainly HMB is synthesized from leucine. Regular supplementation of this compound has a number of benefits: increased lean body mass, anti-catabolic functions, fat reduction, destruction of free radicals and stimulating of the immune system. Despite the many controversies, above mentioned effects are scientifically proven. Improvement of efficiency, endurance and muscle strength in aerobic, anaerobic, or mixed sports is also undeniable.