HMB for muscle injury: Japan RCT shows benefits more likely in long term supplementation Supplementation of HMB for two weeks did not improve muscle injury in elderly suffering from acute mild trauma, said a group of Japanese researchers, but longer term use is likely to be more beneficial. Writing in Nutrients, researchers from Hitachi General Hospital and the University of Tsukuba pointed out that there was no reduction in muscle injury biomarkers or improvement in muscle mass despite HMB supplementation for two weeks. However, they also pointed out that past studies have shown that long-term HMB supplementation ranging from 12 to 48 weeks could produce beneficial results, such as muscle mass gain in healthy elderly.