Creatine Monohydrate

HMB is a metabolite of the essential amino acid leucine. HMB is usually promoted as a muscle-building supplement. It has been claimed to increase strength and lean body mass via an antiproteolytic effect. Recently, of carbohydrate loading as it relates to ameliorating exercise­induced hypoglycemia. HMB has been touted as an endurance enhancer. However, the literature on HMB and endurance performance is scant.

Human Studies

A recent study was conducted by Knitter et al on the effects of HMB on muscle damage after a prolonged run. Thirteen subjects randomly received 3 g/day of HMB or a placebo for 6 weeks. After the training period, all subjects completed a 20-km run. Creatine phosphokinase and lactate dehydrogenase (LDH) activities were measured before and after the prolonged run to assess muscle damage. The placebo group had a significantly greater increase in creatine phosphokinase activity when compared with the HMB-supplemented group. Also, LDH activity was significantly lower in the HMB-supplemented group. These results suggest that supplementation with HMB may prevent exercise-induced muscle damage. However, it is not clear if this could translate into an enhanced endurance performance.

Safety and Toxicity

The use of HMB has been reported to be safe. A summary of safety data was collected in nine studies in which humans were ingesting 3 g of HMB per day. The duration of the studies lasted from 3 to 8 weeks and included young and old, male and female, and exercising and nonexercising subjects. HMB supplementation did not affect any markers of tissue health and function. Furthermore, HMB resulted in a significant decrease in total cholesterol (5.8%), LDL cholesterol (7.3%), and systolic blood pressure (4.4 mm Hg).