HMB Does Not Reduce Exercise Muscle Damage

HMB—known to scientists as beta-hydroxy beta-methylbutyrate—is a metabolite of the essential amino acid leucine. HMB became popular as a muscle and strength building supplement in the 1990s due to speculation that it might limit muscle protein degradation following resistance exercise and enhance positive nitrogen balance. The effects of HMB on muscle and strength gains resulting from resistance training have since been investigated in numerous studies. Some have shown that it is effective, while others have shown that it is not. The majority of studies showing benefits have been poorly designed. A majority of the well-designed studies have shown no benefit. Also, most studies showing beneficial effects of HMB supplementation have involved beginning weightlifters, while most studies involving trained weightlifters have shown no benefit.

More recent studies have looked beyond muscle strength and growth toward other possible benefits of HMB supplementation, but they have also come up empty. The most recent study was performed by researchers at England’s Kingston University and published in the Journal of Strength and Conditioning Research. This study looked at the effect of supplementation with HMB and alpha-ketoisocaproic acid on muscle damaged induced by downhill running. These supplements were found to have no effect on muscle damage biomarkers or muscle soreness in the 72 hours after a 40-minute downhill run.