HMB is an active anabolic compound found in skeletal muscle, which is also formed through the breakdown of leucine. Although it is generally marketed as a muscle and strength builder, the latest research suggests that HMB supplements may be suited for those undergoing high intensity/extended duration training and competition events like CrossFit.
In a most recent publication in the Journal of the International Society of Sports Nutrition, elite rowers (undergoing a heavy training program) who took HMB for 12 weeks had decreased fat mass (over 2 lbs), where there was a slight increase in fat mass in the placebo group. Most pertinent, athletes who took HMB saw a 4% increase in VO2 max (a measure of aerobic exercise capacity) and significant increases in peak power output during exercise testing, where such changes were absent in the placebo group. Such elevations in exercise performance are surprising, considering the subjects were already performing at an elite level.
ACTION POINT: In the past, HMB was prescribed for those just beginning a workout program. However, over the past few years HMB has made a comeback when used at high enough doses and with high intensity training programs. We recommend taking 3 to 6 grams of HMB with a protein shake, 2 to 3 times per day. Make sure one dose is taken 30 minutes preworkout.
Durkalec-Michalski K, Jeszka J. The efficacy of a β-hydroxy-β-methylbutyrate supplementation on physical capacity, body composition and biochemical markers in elite rowers: a randomised, double-blind, placebo-controlled crossover study. J Int Soc Sports Nutr. 2015 Jul 30;12:31.