Supplementing with HMB, a metabolite of the amino acid leucine, was linked to reduced delayed-onset muscle soreness (DOMS) in a study conducted on 24 professional soccer players. The study appeared in the Journal of Pharmaceutical Negative Results.
 
In the study, the researchers recruited a population of 24 professional soccer players who either took a placebo or a daily supplement containing three grams of HMB-FA for two days, once each before a high-intensity resistance training session. Before supplementation and immediately after the exercise protocol, the researchers took blood samples to measure serum creatine kinase (CK) and lactate dehydrogenase (LDH) levels, both indicators of the muscle tissue damage associated with soreness. “High plasma activity of CK and LDH enzymes is commonly used as indicators of muscle tissue damage. It has been demonstrated that these muscle enzymes enter the bloodstream when muscle cells are damaged,” the authors wrote.
 
The placebo group had an average 124.3 U/L CK concentration at baseline, which increased to 332.4 post-test concentration of CK – significantly higher than the increase seen in the supplementation group (122.6 U/L to 211.6 U/L).
 
At baseline, the placebo group had 311.4 U/L LDH concentrations, compared to 424.2 U/L at baseline. The supplementation group only increased from 304.8 to 323.1 U/L of LDH after the exercise protocol.
 
Following the protocol, an intergroup comparison of the data indicated a significant decrease in both CK ad LDH  in the supplement group compared to the placebo group, with this difference achieving clinical significance only after the exercise took place.
 
“The results of this study showed that HMB-FA supplementation reduced muscle injury indices,” the authors of the study noted, but this didn’t result in a significant change to the aerobic fitness index (VO2max) in the short term.
 
While this study did not evaluate possible mechanisms of action, one proposed mechanism for further investigation is that HMB-FA may work by increasing the proliferation and differentiation of satellite cells in fast-twitch fibers, which would increase hypertrophy and alter muscle function. This process also promotes mitochondrial evolution and fat oxidation, according to the authors. Another possible mechanism of action is that supplementation increases the mTOR pathway activation, and increased IGF-1 expression -  the combined pathways are studied for their role in reducing protein breakdown and promoting muscle protein synthesis.
 
According to TSI Group, the suppliers of the HMB ingredient MyHMB, DOMS is most common in people taking part in exercises which they aren’t accustomed to, and often gets worse before it gets better after initial onset over a period of about one or two days.
 
“DOMS can happen at any age and to just about anyone,” said Shawn Baier, MS, MBA, vice president of business development for TSI Group, said. “It can happen whenever you’re engaged in an activity that you’re not used to doing, and that pushes you beyond your usual threshold, be that shoveling snow for the first time in early winter, or suddenly increasing the intensity of workouts.”
 
Across the sum of clinical studies, HMB appears to act through two mechanisms of action, according to Baier. “Its known mechanism of action is to increase protein synthesis and minimize protein breakdown. This dual mechanism has been known to blunt damage to the muscles, meaning that there’s less energy and time required for your body to recover, and you can get back to training harder and sooner. There’s a lot of talk about this on social media from hardcore athletes and weekend warriors.”