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What is HMB Free Acid?

HMB free acid is marketed under the trademark name BetaTOR by Metabolic Technologies Inc. HMB or beta-hydroxy beta-methylbutyrate is a leucine metabolite and can be available as either a calcium salt, or in its free form, known as HMB free acid. HMB free acid has been reported to have superior effects when compared to the regular calcium HMB and as such, is starting to take off as the latest and greatest bodybuilding supplement.

Where does HMB Free Acid Come From?

HMB free acid can be formed in the human body through conversion from leucine. However the conversion process is very slow and inefficient, with only a 5% conversion rate (Van Koevering & Nissen, 1992). Thus, to obtain higher levels, supplementation from synthetic sources is possible.

HMB Free Acid Benefits

HMB free acid shares all the benefits of regular HMB. However, research has shown that HMB free acid in gel form is absorbed up to 97% better, and levels peak in the blood 30 minutes faster. A good analogy to use is the difference between whey protein and hydrolysed whey protein.

HMB Free Acid Benefits for Bodybuilding

One of the most well-known benefits for HMB is that is shows an ability to reduce muscle breakdown or catabolism. Details of this and more can be found in our HMB article. In addition to these, there seems to be many benefits for this ingredient that, as a whole, can help build more muscle, strength, and improve recovery.

HMB Free Acid Benefits for Muscle Building

A study of trained human subjects showed that supplementing with 3 g HMB free acid showed a 252% increase in lean muscle mass, after 12 weeks, when compared to those using a placebo (Wilson et al, 2014). Another study showed that muscle thickness of trained men increased by 14.5% in supplemented subjects after consuming 3g of HMB free acid for 12 weeks, compared to a more modest 4.7% increase in those consuming a placebo (Dunsmore et al, 2012).

HMB Free Acid Benefits for Strength

The benefits of HMB free acid for strength and performance also show equally promising results. Subjects using this ingredient experienced a total increase in bench, squat, and deadlift that was 204% above those who were using a placebo. Their increase in vertical leap power was also 57% higher than unsupplemented individuals (Wilson et al, 2014). The other study showed that supplemented subjects experienced a 18.3% increase in strength compared to only a 6.6% increase for those who were unsupplemented (Dunsmore et al, 2012).

HMB Free Acid Benefits for Recovery

As you would expect, an ingredient that shows promise for preventing muscle breakdown would of course have benefits for improving recovery. A study investigating this issue found that serum creatine kinase, a marker for muscle damage, was almost half as high for supplemented groups after exercised compared to unsupplemented individuals. The supplemented individuals were also able to return to training significantly faster than the other group (Sikorski et al, 2012). The results were evident after supplementing with 3 g/day just a day before training and 30 minutes before training.

With improved recovery, HMB free acid may assist in faster returns to the gym which may also result in faster improvements in muscle and strength gains.

HMB Free Acid Negatives & Side Effects

The safety of HMB has previously been studied. In general, it is a safe compound as it is a normal metabolite of leucine, which naturally occurs in the body. A rat study looking specifically at HMB free acid has found that there were no side effects from consuming high doses of HMB free acid for 91 days. The equivalent human dose would be 402 mg/kg of body weight (Fuller et al, 2014). To put this into perspective, this would be approximately 32 kg of HMB free acid for an 80 kg man, which is over 10 times more than the effective dose.

Perhaps the biggest negative for HMB free acid is that it has, despite its potential benefits, it has not yet reached wide spread acceptance in the bodybuilding supplement community and as of now, it is hard to get your hands on. Given that HMB has always been an expensive ingredient, it is no doubt that HMB free acid would also be a relatively costly addition to your stack.

HMB Free Acid Recommended Doses and Ingredient Timing

From the available studies, it seems that 3 g/day of HMB free acid is the recommended dose. It should be split up into three 1 g serves. If you are training, take one serve 30 minutes before training, and the rest with meals. On rest days, simply take each serve with a meal, spaced though out the day.

HMB Free Acid Supplements

HMB Free Acid or BetaTOR is patented by Metabolic Technologies Inc. This means that they are the sole provider of this ingredient or the time being. There are few large supplement manufacturers that have yet to take up this ingredient in their products. However one noteworthy mention is MuscleTech who will soon be releasing Clear Muscle, their HMB free acid supplement in capsule form. However, until then, the closest we can get is regular calcium HMB. We look forward to the day where HMB free acid is more widely available at an affordable price and accepted within the bodybuilding community.

Stacking HMB Free Acid

HMB free acid can be stacked with a variety of other muscle building supplements like protein powders, creatine, and pre workouts. Creatine combined with HMB free acid may have an additive effect, and is recommended. Prior to using HMB, we recommend having a good set of foundational supplements including a high quality protein powder.

Dunsmore et al (2012), Effects of 12 weeks of beta-hydroxy-beta-methylbutyrate free acid gel supplementation on muscle mass, strength, and power in resistance trained individuals, J. Int. Soc. Sports Nutr. 9:Suppl. 1:P5
Fuller et al (2011), Free acid gel form of β-hydroxy-β-methylbutyrate (HMB) improves HMB clearance from plasma in human subjects compared with the calcium HMB salt. Br J Nutr 105(3):367-72.
Fuller et al (2014), Rathmacher, 2014 Subchronic toxicity study of β-hydroxy-β-methylbutyric free acid in Sprague-Dawley rats, Food Chem. Toxicol. 67:145-153
Sikorski et al (2012), The acute effects of a free acid beta-hydroxy-beta-methylbutyrate supplement on muscle damage following resistance training: a randomized, double-blind, placebo-controlled study, J. Int. Soc. Sports Nutr. 9:Suppl. 1:P27
Van Koevering M, Nissen S (1992), Oxidation of leucine and alpha-ketoisocaproate to beta-hydroxy-beta-methylbutyrate in vivo. Am J Physiol. 262(1Pt1): E27-31
Wilson et al (2014), The effects of 12 weeks of beta-hydroxy-beta-methylbutyrate free acid supplementation on muscle mass, strength, and power in resistance-trained individuals: a randomized, double-blind, placebo-controlled study. European Journal of Applied Physiology Eur. J. Appl. Physiol. FV:1-11

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