Accelerated Muscle Repair and Function W/ 10-15g High Leucine EAA Supplement | Shouldn't Whey do the Same?

Would it be advisable to switch from the large scoop with protein (red) to the small one with (EAAs) or take both? That's a question today's SuppVersity article may help you to answer on your own.

Yes, leucine stimulates mTOR; but no, on its own, it is not going to build muscle, significantly accelerate muscle repair and function. Why's that? Well, your muscles are not made of leucine only. You also need the other essential amino acids histidine, isoleucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

Hiroyuki Kato et al., researchers from the Frontier Research Laboratories in Japan know that... obviously, after all, they work for the world's #1 amino acid producer, Ajinomoto Co., Inc. That makes them potentially biased, but that's a bias they openly declare.
I would thus suggest we take a careful look at study design, results and - this is where a bias will usually "sneak" in - the authors' interpretation of their results, i.e. "that leucine-enriched amino acids accelerate recovery from muscle damage by preventing excessive inflammation" (Kato. 2016) before we discard their study as 'amino acid advertising'.

Figure 1: Overall experimental design. Rats treated with distilled water (EC-Con, n = 24) and leucine-rich essential amino acids (EC-AminoL40, n = 25) underwent electrical stimulation under anesthesia to induce five sets of 10 eccentric contractions. Sedentary rats (n = 24) treated with distilled water were used as control. (Kato. 2016).

The first downside of the study is the hairy 'subject group'. With 8–9 weeks old Sprague-Dawley rats we are dealing with yet another dreaded rodent study - one that allows scientists to do something you simply cannot do in humans: cut away their tibialis anterior muscle. That's also why I personally find it more disappointing that there was only a water control, no group that received an intact protein with a high EAA content, such as whey protein. The comparison of ...

• water with 1g/kg of a 60% leucine, 40% other amino acid mix to
• plain distilled water as a control

Figure 2: No, the size gains after a single muscle-damaging bout of exercise were not significant (left). The time-course of torque and thus muscle function recovery, on the other hand, was - with a full recovery within the 14-day study period only in the supplement group (Kato. 2016).

And yes, this means that we can expect to see similar trends in muscle weight (Figure 2, left | note: the "gains" after 14 days are obviously non-significant in response to only one simulated workout), maximal torque and thus your potential physical performance (Figure 2, right); or, as the scientists phrase it:

"[W]e found that leucine-enriched essential amino acids also alleviated muscle dysfunction, which is correlated with the extent of muscle damage. Notably, these amino acids restored full muscle function [you can see that in the muscle torque data in Figure 2] 14 days after eccentric contraction without a [significant] increase in muscle mass" (Kato. 2016).

Figure 3: The benefits occur early during the recovery process (Kato. 2016).

For the previously outlined reasons you can also expect that whey protein will have at least as pronounced effects on the recovery from muscle damage you can marvel at in Figure 3 and the post-exercise changes in inflammatory cytokines and genes that eventually drive the formation of new myotubes that can be used for both, muscle repair and growth. That the latter can be significantly enhanced with whey protein when it is administered in conjunction with repeated, well-planned resistance training, has been confirmed in dozens of studies. There's some evidence that similar benefits can be achieved with EAAs (not BCAAs!), but the obvious question is...
References:

• Kato, Hiroyuki, et al. "Leucine-enriched essential amino acids attenuate inflammation in rat muscle and enhance muscle repair after eccentric contraction." Amino acids (2016): 1-11.