It is believed that athletes use the leucine metabolite HMB to promote skeletal muscle mass to increase athletic performance. As an ergogenic aid, it is used by strength and power athletes, bodybuilders, and athletes in high performance sports. There is also evidence to suggest that HMB plays a role in specific physiological and biochemical variables in relation to metabolic demands during athletic competitions.
Although not clearly understood, it has been demonstrated that leucine has anti-catabolic properties. This means that the metabolite of leucine, HMB, appears to contribute to these results by decreasing muscle breakdown. Thus, the ingestion of a dietary supplement containing HMB may promote an increase in the rate of total body protein synthesis and suppression of protein degradation. This anabolic effect can be attributed to the increased contribution of amino acids to skeletal muscle. In particular, leucine, a branched chain amino acid, has the ability to independently stimulate protein synthesis and thus act as a regulator of protein metabolism.
There is evidence that untrained men and women who are involved in a 3 to 4 week resistance training program show a higher gain in lean body mass and strength with doses of 1.5 to 3 grams per day of HMB. It has also been shown that elderly men and women who engaged in a beginner training program for 8 weeks with supplementation of 3 grams per day of HMB, experienced a significant increase in lean body mass and in 1RM strength, and a decrease in fat mass.
In regard to trained athletes it has been reported that supplementation with HMB (3 grams per day) resulted in a significant change in muscle function with respect to strength and body composition in response to intense resistance training. A significant increase in lean body mass occurred, whereas the strength in trained athletes have less potential for an increase when compared to untrained athletes.
It is indicated that supplementation with HMB can increase lean body mass, strength gains associated with resistance training in already trained athletes of high performance. The exact mechanism by which this can occur is still unknown, but studies also indicate that there may be a decrease in skeletal muscle damage. (Journal of Exercise Physiology, Vol. 16:1, Feb. 2013)