HMB-FA Study: Improve Strength, Power & Lean Mass?

*originally published on

If you’re like most people, you’ve probably never heard of HMB before. HMB, also known as beta-hydroxy-beta-methylbutyrate, is a metabolite of the amino acid leucine, which is believed to enhance the repair of damaged muscle tissue as a result of exercise.1 Despite the fact that HMB is not very well known, its use has been studied since 1996 with numerous studies demonstrating positive effects on lean mass and strength gains, particularly in untrained individuals.

More recently, results from a new study on HMB supplementation — published in the February 2014 edition of the European Journal of Applied Physiology — reaffirmed previous findings by replicating increases in strength, power, and lean body mass in the HMB group. 2

That all sounds great, sign me up. Well, maybe not so fast…let’s look into the study further before we jump to any definitive conclusions.

What Exactly Was Studied?

muscle gaining supplements20 men participated in the study and were randomly placed into a group that either received the HMB supplement or a placebo. For this study, a different formulation of HMB was used — specifically the free acid form (HMB-FA), which gets into the bloodstream much quicker and at lower doses than standard HMB (this form is bound to calcium, HMB-Ca).

The goal was to see what effect supplementation with HMB-FA had on people with resistance training experience during a periodized resistance-training program.What exactly is a “periodized” program? Basically, it’s a fancy way to say that the workout plan varies the weight and reps/sets used over time — this type of plan is generally used for people who have more experience lifting weights. Diet was controlled under the supervision of a registered dietician and all workouts were performed under the supervision of the researchers to ensure that everything was done correctly.

What did the researchers actually test for? Differences in skeletal muscle hypertrophy, body composition, strength and power between the HMB and placebo groups. In addition to those measures, the researchers also looked at how the HMB-FA affected performance in an overreaching phase. If you’re not familiar with that term, an overreaching phase is basically a planned period of training that has significantly increased stress with the end goal of seeing larger improvements at the end of a training cycle. The overreaching period lasted two weeks and was followed by a two week taper where the intensity of the workouts was decreased significantly.

What About The Results?

HMB-FA had a positive impact across the board on strengthpeak power, and lean body mass, including an attenuation in strength decreases during the overreaching phase.

If we dig a bit deeper into the results, there is an interesting finding — it appears that HMB-FA was particularly beneficial during the overreaching phase (weeks 9 and 10 of the study). If you refer to the graphs below, it is quite easy to see that much of the differences between the HMB-FA group and the placebo can be attributed to the final phase of the study which incorporated overreaching.

There were certainly differences seen in the HMB-FA group prior to the overreaching portion of the study, but that time window seems to be the point where the HMB group had the largest improvements compared with the placebo group. This makes sense considering that HMB is particularly known for its anti-catabolic effects and functions with respect to the repair of damaged muscle tissue.


When considering the latest research, it is always important to ask: is this applicable to me?

If you are a male who is experienced with resistance training, specifically who has utilized a periodized program with overreaching, then yes, you will likely benefit from HMB-FA. Based on what we know from previous studies, combined with the study analyzed here, HMB is likely a beneficial supplement for those looking to improve strength and body composition.

That said, we simply need more high quality research to definitively support its use. At the moment HMB-FA is not available for purchase, although we suspect if more research like this follows suit with similar results it will be a hot a supplement in the coming years. *Updated on 2/5/16: HMB-FA is available for purchase online.

References   [ + ]

1.Wilson GJ, Wilson JM, Manninen AH. Effects of beta-hydroxy-beta-methylbutyrate (HMB) on exercise performance and body composition across varying levels of age, sex, and training experience: A review. Nutr Metab (Lond). 2008;5:1.
2.Wilson JM, et al. 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. Eur J Appl Physiol (2014)