Sep 17, 2018
In 2009, research by Atherton and colleagues assessed the effects of essential amino acids (EAA’s) and their impact on anabolic signalling.
The group discovered that key signals for muscle growth, being mTORC-1 and 4EBP1 increased in response to the amino acid 'leucine', but not in response to any other EAA. In addition, the important signal of p70S6K1 was increased by all EAA’s (with the exceptions of isoleucine and valine), but three times more-so with leucine enrichment .
With this and many other papers emerging in the field, demonstrating the anabolic effects of leucine, this protein became chief among the EAA’s for increasing the synthesis of contractile proteins.
When ingested, leucine is broken down into alfa-hydroxy-isocaproic acid (α-HICA) and β-hydroxy-β- methylbutyrate (HMB), with both being suggested to offer anabolic benefit.
It was shown that consuming 1.5g of α-HICA in young soccer players increased lean mass and reduced markers of muscle damage, compared to placebo. This was shown, despite players consuming sufficient protein to maximise muscle growth .
At present, this is the only published study on this leucine metabolite.
Five percent of leucine metabolism is converted into HMB.
We’ve known of the potential anabolic benefits of this leucine metabolite since the mid 1990s. Seminal work by Nissan and colleagues revealed that HMB in the calcium form (HMB-Ca), in combination with resistance training, increased muscle mass and improved strength in untrained men .
A decade on and with more trained subjects being assessed, the ergogenic benefits started moving from hot to lukewarm.
In a meta-analysis in 2009 by Rowlands and Thomson, it was concluded that HMB supplementation would offer a small, positive effect on strength performance in untrained subjects, but no such effect occurred in trained subjects, along with trivial effects on increases in muscle mass in both groups .
A further review in 2013, highlighted that HMB may offer a benefit towards reducing exercise-induced muscle damage and prevent muscle loss during states of chronic disease .
By the end of 2013, this was the general, consensus for supplemental HMB.
Just one year later...this consensus changed.
In a series of studies conducted from the same group by Wilson et al. (2014) and Lowery et al. (2016) on a new supplemental form of HMB (HMB-FA), the group showed unprecedented ‘steroid like gains’ in trained lifters . However, these papers since have been heavily critiqued by fellow experts in the field on scientific grounds .
In the most recent consensus statement by the International Olympic Committee (IOC), the benefits attributed to HMB were concluded as being likely achieved by simply maintaining protein intakes at the current set recommendations for maximising muscle hypertrophy (1.6g.kg.bw).
With this in mind, the researchers of today’s paper wanted to assess the effects of consuming 'off the shelf' leucine metabolite supplements in conjunction with a resistance training program on muscle thickness and performance. Importantly, the researchers wanted to see if such benefits would occur in the presence of an energy sufficient diet and a daily protein intake that’s been suggested to maximise muscle anabolism.
Join me for the next 30 minutes, as I review this great paper and share with you some important take home that will improve your knowledge on the effects of leucine metabolites on body composition and performance.
Special thanks to the great researchers of this paper: Filipe Teixeira, Catarina Matias, Cristina Monteiro, Maria Valamatos, Luís B Sardinha and Stuart Phillips.
References attached in FB post.