Refereed Papers

Twenty-three trained men took either a single (3 g) dose of HMB free acid or a placebo 60 minutes before undergoing a single bout of high-intensity exercise.  The exercise bout resulted in muscle swelling, decreased jump performance, and decreased force production in both groups, but the participants’ highly trained status allowed for a quick return to normal (within 24 h).  However, the single dose of HMB free acid significantly improved recovery of work capacity; the men who took HMB recovered work capacity in just 24 hours, while the placebo group had not yet recovered at 72 hours.  Thus, even a single dose of HMB free acid allowed the participants to recover to their full training capacity much sooner after a strenuous, high intensity training session.

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.

Elite infantry soldiers were supplemented with either HMB free acid (BetaTOR) or a placebo and underwent an advanced military training, which consisted of periods of restricted sleep and severe environmental stressors.  Over the 23-day study the researchers saw a decrease in the insulin growth factor binding protein number 7 (IGFBP-7).  The reduction in this protein indicated a reduced stress response, and warrants further investigation into the physiological role of HMB free acid (BetaTOR) in reducing stress during intense military training protocols.

Healthy men supplemented with HMB free acid (BetaTOR) (3 g/d) and underwent a six week resistance training program.  BetaTOR supplementation improved the anabolic adaptations (GH/IGF-1) and decreased catabolic stress hormones (cortisol/ACTH).  Similar to previous studies BetaTOR supplementation also improved strength and power during the training when compared to placebo-supplemented men. 

This paper reviews the first nine studies conducted in humans with HMB free acid through 2016.  The studies involved resistance training protocols and high intensity interval training (HIIT).  HMB free acid was shown in all of the studies to improve outcomes by improving recovery, improving performance (aerobic metabolism and strength), increasing lean muscle mass and decreasing fat mass, and improving immune and endocrine response to intense exercise.  These studies demonstrate the utility of HMB free acid as an ergogenic aid for muscle over a variety of exercise regimens. 

Military training is some of the most strenuous training an individual can undergo.  Sleep deprivation coupled with a high level of continuous activity and heavy physical load carriage not only wears down the soldier’s muscular strength, but can also invoke an inflammatory immune response stimulating catabolic processes in muscles.  In this study of soldiers undergoing military training, HMB free acid supplementation (BetaTOR) decreased TNF-α, IL-6, and IL-8, key inflammatory markers.  This decrease in inflammation likely resulted in the increase in muscle quality the authors also measured.  In conclusion, BetaTOR supplementation reduced the inflammatory response and allowed the soldiers to maintain muscle quality during the high intensity military training.  

High-Intensity Interval Training (HIIT) is an effective training routine that has recently gained much popularity.  In this study untrained men and women participated in a 4-week HIIT training regimen and were supplemented with either a placebo or beta-hydroxy-β-methylbutyric acid (BetaTOR®).  Thirty-seven men and women completed the double-blind, placebo-controlled study which also included a non-exercise control group.  The participants underwent 12 sessions of cycle ergometer-based HIIT.  Participants supplemented with 3 g of BetaTOR per day maintained a greater physical working capacity at fatigue onset when compared with the placebo group.  This study demonstrates that during strenuous HIIT training BetaTOR supplementation improves endurance performance.

The free acid form of HMB (BetaTOR) is available in commercially produced capsules similar to that of CaHMB.  Therefore this study was conducted to compare the pharmacokinetics of HMB free acid (BetaTOR) with CaHMB when both were administered in commercially manufactured capsule form.  The results of this study demonstrated that when the capsule delivery form was used for both the HMB free acid (BetaTOR) and CaHMB, plasma HMB levels were greater and peaked earlier, and HMB clearance from the plasma was greater with HMB in the free acid form.  This advantage allows athletes to better gauge the delivery timing of HMB intake in relation to exercise bouts.

In this study the researchers looked at the endocrine response after an acute heavy resistance exercise protocol.  Twenty resistance trained subjects were randomized to receive either 1 gram of HMB free acid or a placebo 30 minutes before the exercise bout.  Endocrine responses from pre- to 30 min post exercise were measured.  The researchers observed that both growth hormone (GH) and insulin like growth factor-1 (IGF-1) area under the curve were increased with the HMB free acid in comparison to the placebo group.  These findings further demonstrate how HMB supplementation potentiates and increases the anabolic response of resistance exercise. 

This study was conducted with college-aged men and women supplemented with HMB free acid (BetaTOR).  Subjects underwent High Intensity Interval Training (HIIT) 3 times per week for 4 weeks.  HMB free acid supplementation improved the gains in VO₂peak and ventilatory threshold compared with placebo supplementation.

This 12 week study in highly trained men, undergoing a rigorous periodized training program, demonstrated that supplementation with HMB in free acid form resulted in increased gains in strength, power, and lean mass over placebo and training alone.  Additionally, the researchers conducted a 2 week overreaching protocol in weeks 9 and 10 to simulate overtraining.  HMB free acid minimized or eliminated losses in strength and power during this period and allowed for improved recovery after intense training.

A 91-day subchronic toxicity study was conducted in male and female Sprague-Dawley rats following FDA Redbook protocols.  Rats were assigned to HMBFA treatments at either 0, 0.8, 1.6, or 4% of the diet by weight. The no-observed-adverse-event-level (NOAEL) was determined to be 4% of the diet, which corresponds to an intake of 2.48 and 2.83 g/kg BW d-1 in the males and females, respectively.  Using body surface area conversion, the equivalent dosage in humans would be 402 and 459 mg/kg BW d-1 for men and women, respectively.

This study examined the effects of HMB free acid (HMB-FA) supplementation and cold water immersion (CWI) on recovery in 40 resistance-training men post high-intensity lower body training. HMB-FA and HMB-FA combined with CWI resulted in significantly lower C-reactive protein levels during recovery. More importantly HMB free acid combined with CWI resulted in a significant improvement in power per repetition. The authors concluded that HMB-FA combined with CWI improved performance recovery after the acute bout of exercise.

In this study the effects of HMB free acid supplementation and cold water immersion (CWI) on the expression of complement receptor type 3 (CR3) and the concentration macrophage inflammatory protein (MIP-1β) were studied after intense resistance exercise.  It was clear that both CWI and HMB free acid attenuated CR3 expression.  While these were not correlated with an objective measure of improved recovery, the researchers concluded that HMB free acid modulates the inflammatory response which could help the muscle recover faster.

The effects of HMB free acid supplementation and cold water immersion (CWI) on immune response after intense resistance training was studied in forty male subjects. Supplementation with HMB free acid reduced the pro-inflammatory cytokine TNF- immediately post exercise and its receptor expression (TNFR1) during the recovery period compared with placebo or CWI. The researchers concluded that HMB free acid may attenuate the immune response to resistance exercise which may then lead to reduced recovery time.

This publication is the International Society of Sports Nutrition position stand on the efficacy of HMB use in sports nutrition and combines a comprehensive review of HMB with the official position of the ISSN on HMB use. The position statements included in this paper were reviewed and approved by the Research Committee of the ISSN. Based upon this comprehensive review of HMB literature, the primary position statements were that HMB enhances muscle recovery by attenuating muscle damage; HMB increases muscle hypertrophy, strength, and power in trained and untrained populations when the appropriate exercise protocol is applied; HMB efficacy is manifested in young and old; and HMB is safe to consume.

This study in trained athletes demonstrated that HMB free acid taken before a muscle-damaging, resistance-training session decreases muscle damage and improves perceived readiness to train in the next session. Thus, the athletes were able to recover quicker and train harder sooner with HMB free acid supplementation.

Skeletal muscle protein turnover was measured in healthy young men in response to an oral dose of either 2.4 g of HMB in free acid form or 3.4 g of leucine. While both HMB and leucine stimulated muscle protein synthesis, HMB was also shown to attenuate muscle protein breakdown (-57%). The authors concluded that HMB induces anabolic effects in skeletal muscle that are distinct and/or additive to the effects of leucine.

The overreaching cycle during a resistance-training program is designed to simulate muscle stress that is encountered during higher intensity training, peaking for competition, or multiple-game tournaments. In this study, trained athletes underwent a 2-week overreaching cycle after 8 weeks of intense resistance-training. HMB free acid supplementation resulted in decreased CPK, an indicator of muscle damage; decreased cortisol, a stress hormone; and maintained more strength throughout the overreaching cycle. In conclusion HMB free acid provided more muscle protection against the sudden increase in training intensity compared to the placebo.

This is the first 12-week study using the new delivery form of beta-hydroxy-beta-methylbutyrate, HMB free acid. Highly trained athletes underwent an intense, high-volume, resistance-training program, including a 2-week overreaching phase during weeks 9 and 10. HMB free acid supplemented subjects had greater strength gains, increased Wingate power, and increased muscle thickness compared with the placebo supplemented subjects. This study showed that even in highly trained athletes, HMB free acid results in greater training gains over a 12-week periodized resistance-training program.

This is the first resistance training study to examine the acute effects of HMB free acid supplementation on muscle damage and perceived recovery scale (PRS) when initiating a high-volume resistance-training program. The results showed that when compared to placebo, HMB free acid resulted in decreased CPK indicating decreased muscle damage, and an increase in PRS meaning the subjects felt more recovered 48 hours after the training. In conclusion, HMB free acid minimized the initial muscle damage and improved recovery in trained athletes initiating a high-volume training program.

The results of this research study demonstrate that a liquid gel form of HMB is more readily available to tissues when taken orally than the currently available powdered form, Calcium HMB. The results show quicker and higher plasma levels of HMB with improved utilization by the tissues. HMB free acid gel could improve HMB availability and efficacy to tissues in health and disease.