Infinite One Series: HMB Supplement Review
β-Hydroxy-β-methylbutyrate (HMB) is a metabolic derivative of the amino acid leucine. HMB is known to increase muscle protein synthesis through mTOR signaling pathways while concurrently reduce catabolism. Studies utilizing HMB supplementation in trained populations are limited. Under normal conditions, ~5% of leucine consumed is converted in the body to HMB. Overall, the preliminary results suggest that supplementation of HMB with 1.5 to 3 g·day-1 of can increase fat-free mass and strength in a resistance-training program. It can be found in nature, but it is difficult and impractical to get on a regular basis, for example, 3 grams per day. Therefore, supplementation may be beneficial for strength training practitioners or those under extreme muscular stress who want to improve athletic performance. If you look at the research, there is a staggering amount of research to support the validity of HMB for increasing lean muscle mass and improving performance:
– Vukovich et al. reported that eight wks of supplementation with HMB-Ca (3 g·day-1) significantly increased lean body mass and promoted 1 RM strength increases in a group of elderly men and women beginning a training program.
-Gallagher et al. analyzed the effects of HMB-Ca supplementation (3 and six grams per ·day) for 8 wks of resistance training on a group of untrained men and noticed that there was a significant decrease in markers of muscle damage (i.e. creatine kinase) with an increase in lean body mass in the 3 g·day-1 group.
Ferreira et al. reported a significant increase in lean body mass and strength gain associated with resistance training in elite kayakers when supplemented with three grams·day-1 HMB-Ca.
It has recently been suggested that β-hydroxy-β-methylbutyrate-Ca (HMB-Ca) increases fat-free mass and strength gains during resistance training in adults. Researchers in a recent double-blind, placebo-controlled study assessed the effects of HMB-Ca (37.5 mg·day-1) on body composition, athletic performance, and inflammatory mediators in 20 elite canoeists. The athletes were supplemented and followed for a period of 12 wks during strength training. Throughout the study, the athletes participated in all training sessions with individual workloads.
The training sessions consisted of an average of 6 hrs·wk-1 of resistance training (e.g., 1 to 3 sets of 2 to 8 repetitions at intensities ranging from 80 to 95% of 1 RM) that was performed on Monday, Wednesday, and Friday as well as 10 hrs·wk-1 of sprint-specific training and technical assistance with the boat, averaging two daily sessions for a total of 11 training sessions per week. At the end of the study, supplementation with HMB-Ca at a dose of 37.5 mg·day-1 per body increased lean body mass in conjunction with strength gains when associated with resistance training in trained, high-performance athletes.
The mechanism by which this occurs is still unknown, but the results indicate that there might be a decrease in skeletal muscle damage. There was greater improvement in the athletic performance response in the supplemented group. While research to date is encouraging, there is a definite need for more tightly controlled and long-term studies to verify whether HMB-Ca supplementation can be effective in improving the strength and development of muscular hypertrophy associated with resistance training and using the same supplementation in free acid (HMB-FA) form and in different dosages. The results indicated that a dose of HMB-Ca could potentiate an increase in lean body mass commensurate with strength gains associated with endurance training in competitive athletes. The mechanism by which this occurs is still unknown, but the results indicate that supplementation might decrease the damage to skeletal muscle when stressed before training with a significant difference in serum creatinine.
β-Hydroxy-β-methylbutyrate (HMB), a leucine derived metabolite, has been demonstrated to augment strength and lean muscle gains when supplemented in conjunction with resistance training. While HMB has displayed robust anabolic/anticatabolic properties, the underlying mechanisms regarding its efficacy are not completely understood. Recently, an 18% increase in strength gain was demonstrated following 12 weeks of HMB ingestion compared to placebo in experienced resistance trained men.
To examine the endocrine response to a bout of heavy resistance exercise following acute β-hydroxy-β-methylbutyrate free acid (HMB-FA) ingestion. Twenty resistance-trained men were randomized and consumed either 1 g of HMB-FA or placebo, 30 minutes before performing an acute heavy resistance exercise protocol. They put the men through their paces with leg training exercises: squats, dead-lifts and split-squats. Blood was obtained before, immediately after, and 30 min after exercise. The researchers examined circulating concentrations of testosterone, growth hormone (GH), insulin-like growth factor (IGF-1), and insulin. At the end of the study, the resistance exercise protocol resulted in significant elevations from in testosterone, GH, and insulin. HMB supplementation had no effect on insulin and testosterone but did have an impact on increasing growth hormone and IGF-1. The researchers concluded that HMB-FA before resistance exercise augmented the GH response to high volume resistance exercise compared to placebo. The researchers suggested that HMB-FA might increase the GH/IGF-1 axis through similar pathways as its leucine. Leucine has also been demonstrated to stimulate modest increases in GH concentrations when taken orally. The results of this study also provide evidence supporting a potentially greater anabolic response associated with HMB supplementation. These findings provide further support for the potential anabolic benefits associated with HMB supplementation. Considering that one of the physiological roles of GH is to stimulate fat burning, the significantly greater GH response in HMB-FA may provide further insight for the changes in body composition observed in several studies examining the efficacy of HMB.