Protein Timing Reloaded: A Reminder on the Importance of Repeated 20g Pulses for Optimal Protein Synthesis

Protein timing & dosage matter for protein synthesis in the PWO window.

"30g+ of quality (=leucine rich) protein per meal." I am not really sure how often I have been writing and saying this here, on facebook and on the Science Round Up at SuperHumanRadio in the past months, but I hope that it's been enough for you to remember this simple rule; a rule that will also help you to distribute your protein intake somewhat more evenly across the day and thus - as a recent study that was conducted by researchers from the School of Medical Sciences at the RMIT University, in Melbourne, the Australian Institute of Sport in Canberra, the Department of Kinesiology at the  McMaster University in Hamilton, Ontario and the Nestlé Research Center in Lausanne, Switzerland - maximize the protein induced increase in protein synthesis.
More is only more if it's adequately timed & distributed

The scientists knew from countless previous experiments that a single bolus of∼20 g of protein after a bout of resistance exercise would provide a maximal anabolic stimulus during the early post-exercise recovery period (∼5 h). The "effect of various protein feeding strategies on skeletal muscle protein synthesis during an extended recovery period (12 h)" (Areta. 2013) was yet largely  unknown. In order to shed some light onto the protein-anabolic response in this "post-post-workout window", the researchers compared three different patterns of ingestion of 80 g of protein during 12 h recovery after resistance exercise and the associated anabolic response in human skeletal muscle:

• 10, 20 or 40 g feedings using a pulsed, intermediate or bolus ingestion regimen, respectively
• consumed after 4x10 reps @  80% of the 1 RM with 3 min rest between sets

 In accordance with the hypothesis that protein timing would directly influence the expression of "anabolic" signalling proteins in the muscle, the researchers observed significant hierarchy with BOLUS > INT > PULSE in the magnitude of phosphorylation of p70S6K and p-AKT on an individual base.

Figure 1: Fractional protein synthesis expressed relative to mean protein synthesis at the respective timepoint (left); corresponding levels of the "anabolic" signaling proteins p70S6K (right, top) and p-akt (right, bottom; Areta. 2013)

However, despite the fact that the immediate response was maximal in the BOLUS group, both the actual amount of protein that was shuttled into the muscle was still significantly higher in the INT trial, in the course of which the subjects ingested 20g of protein every three hours.

So what's the deal, then?

The "anabolic window" turns out to be more of a barn door, which is unlocked by the key of exercise and nutrition science (learn more)

In their discussion of the results, the researchers point out that this is the first study to confirm the long-touted notion that ...

"[...] rates of myofibrillar protein synthesis (MPS) remain elevated above rest throughout 12 h of recovery when a single bout of resistance exercise is followed by the partitioned ingestion of 80 g of high quality protein. Furthermore, we show that daily rates of protein synthesis were highest with regular (i.e. every 3 h) intake of a moderate (20 g) quantity of rapidly digested whey protein." (Areta. 2013)

Areta et al. specifically emphasis that the acute stimulation of the nutrient and contraction-sensitive intracellular signalling network is thus not the main determinant of net protein synthesis in the huge post-anabolic window.
The anabolic effects of the intermediate supplementation do yet only appear to be. Over the whole study period, they are not statistically different and the superiority in terms of the actual fractional protein synthesis (FSR) persists, even when using a mean intracellular enrichment from the other groups. Thus an increase in intracellular enrichment cannot be the underlying mechanism for the increase in  fractional synthesis rates in the intermittent supplementation trial (INT) the researchers ascribe to an optimized interplay between resistance exercise, time between ingestion, and the total quantity (20g = at the critical threshold) of each (whey) protein feeding. The optimally timed and adequately dosed ingestion of 4 servings of 20g of whey could thus have

Figure 2: Plasma EAA concentration following a bout of leg extensions and subsequent whey ingestion during a 12 h recovery period (top); timing and dosage of supplementation (bottom); p < 0.05 for pulse *, intermittent †, and bolus ‡ at equivalent time point (Areta. 2013)

"[...] resulted in a cyclical plasma AA profile that might be considered ideal to stimulate MPS [...] While the temporal resolution of time points selected for quantifying plasma amino acid concentrations failed to clearly show distinct amino acid profiles throughout the 12 h post-exercise period a hierarchical response was observed for leucine concentration early in recovery indicative of an initial divergence in branch-chain amino acid availability between feeding patterns [figure 2]. Thereafter, the continuous hyperaminoacidaemia or lack of postprandial periods of relative hypoaminoacidaemia over the 12 h period with PULSE feeding most likely resulted in some suboptimal stimulation of the protein synthesis machinery similar to that observed with continuous amino acid infusion." (Areta. 2013). 

Now, this may appear counter-intuitive at first, after all the aminoacedemia in the intermediate trial does not appear to be more pronounced than that in the pulse trial and certainly inferior to the one of the bolus trial. This is in fact true, but it is a mere consequence of much greater %-ual absorption of the amino acids in the intermittent trial compared to both the bolus and pulse supplementation, of which the former are 'protein wasting' and the latter simply insufficient to fully trigger the protein synthetic response.

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Bottom line:  It should not really be necessary that I actually formulate another bottom line. If you stick to my basic recommendations (outlined among others in my interview with my buddy Sean Casey) you will do something very similar with your 3-5 meals with 30+g of quality protein each. The only thing that may be worth adding to it is a re-emphasis on the interaction of timing and dosing. 

You need at least 20g of leucine-rich protein to kickstart protein synthesis and - as of now - it looks like those will not sustain maximal protein synthesis for longer than ~3h before you have to 'refuel' the amino acid pool and (probably more imporatantly) 'reignite" the protein synthetic machinery with another 20g+ bolus of whey.

In view of the fat that proteins with a low(er) leucine content will probably need to be ingested in higher amounts I would still stick to the '30g+ rule' - after all, I assume you won't want to live off whey protein supplements and Quest Bars, only - do you?

Important additional read: "Evidence From the Metabolic Ward: 1.6-2.4g/kg Protein Turn Short Term Weight Loss Intervention into a Fat Loss Diet" | read more...

References: 

• Areta JL, Burke LM, Ross ML, Camera DM, West DW, Broad EM, Jeacocke NA, Moore DR, Stellingwerff T, Phillips SM, Hawley JA, Coffey VG. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis. J Physiol. 2013 May 1;591(Pt 9):2319-31. doi: 10.1113/jphysiol.2012.244897. Epub 2013 Mar 4. 
• Moore DR, Areta J, Coffey VG, Stellingwerff T, Phillips SM, Burke LM, Cléroux M, Godin JP, Hawley JA. Daytime pattern of post-exercise protein intake affects whole-body protein turnover in resistance-trained males. Nutr Metab (Lond). 2012 Oct 16;9(1):91.