In a comprehensive review of HMB studies over the past two decades, the authors examine HMB efficacy. This review also examines why many newer studies, longer in length than some of the original studies and also conducted with HMB in the free acid form, are suggestive of stronger efficacy in both trained and untrained populations. The authors concluded that recent studies utilizing high-intensity training have demonstrated HMB efficacy in maintaining muscle mass and attenuating the inflammatory response. In particular these studies show improved efficacy of HMB free acid in trained athletes.