Pre Workout Protein Supplementation 101: Slow or Fast, Bolus or Pulse? Protein Synthetic Response is Identical!

Should she drink her protein shake all at once or in 33ml gulps every 15min, if she has it before her workout? And wait, wouldn't it be better to have the shake afterwards, anyway? A recent study provides some answers.

I don't know if you notices, but it has been a while since the last study from the Exercise Metabolism Research Group at the Department of Kinesiology of the McMaster University in Hamilton, Ontario, Canada, hit the SuppVersity news. Allegedly, I mentioned Stuart Phillips only a couple of days ago, when I referenced the West study on "Associations of exercise-induced hormone profiles and gains in strength" (West. 2012), in the context of the questionable significance of post-exercise increases in testosterone levels, as far as muscle and strength gains are concerned - for those who missed that, it was  in the "Anabolic Workouts Revisited" post from last Monday. That was however about it as far as the news of the last weeks are concerned. So I was already wondering, when the first of you would be showing initial signs of "acute protein synthesis in response to protein ingestion study withdrawal symptoms", when I hit onto the latest study Phillips' group at McMasters participated in. The lead author of the study is however Louise M. Burke who's currently working at the Australian Institute of Sport in Canberra, Australia.

What happens if you ingest your post-workout protein before the workout ;-) ?

The aim of the study, of which the authors explicitly state that it is a quasi-followup to previous results which have conclusively identified fast acting protein sources (mostly whey, in some instances EAAs) as superior triggers, or I should say, promoters of post-exercise protein synthesis, was

"[...] to investigate the effects of manipulating patterns of aminoacidemia from protein sources consumed before a bout of resistance exercise bout." (Burke. 2012)

To this end, Burke et al. simulated the ingestion of slow or fast protein sources by bolus vs. pulse feeding of a leucine-enriched (+5g) whey protein drink (Nestec by Nestlé, sponsor of the study; the reason for the enrichment was to make sure that there would be a decent amount of leucine in each pulse serving).

• Bolus (B) - 1 x 500ml w/ 25g whey + 5g leucine drink, 14 x 33ml placebo every 15 min
• Pulse (P) - 1 x 500ml placebo drink,  14 x 33ml w/ 1.79g whey + 0.36g leucine each
• Placebo - 1 x 500ml placebo drink, 14 x 33ml placebo drink

The subjects, 12 resistance-trained men (age: 27y; body mass: 94.3kg; 1 RM single leg ext.: 42.8kg) with greater than 2 yr of experience of regular (at least twice per week) strength training, who had followed a standardized diet before each of the testing sessions (energy content of 80kcal/kg BM; 45%/34%/21% of the energy from carbs/fats/protein), started consuming their large 500ml beverage and the subsequent 14 small 33ml servings (every 15 min) 45min before they performed a standardized leg training session:

"This bout consisted of a  standardized warm-up, followed by 10 sets of 8–10 repetitions of leg extension at a workload equivalent to 80% of the specific leg 1 RM with 2-min recovery between sets. The leg that performed exercise was alternated for each trial. The duration of the resistance bout was approximately 45 min." (Burke. 2012)

Before during and after the exercise bout blood samples were collected. Muscle biopsies from the vastus lateralis of the exercised leg were taken 45min before, as well as after 1 h and 5 h of recovery.

Figure 1: Serum leucine and insulin levels after bolus and pulse ingestion, expressed relative to placebo group (left) and fractional protein synthesis rate (in %/h) during the 5h following the rest period after the workout (right; based on Burke. 2012)

As you can see in figure 1 the results basically confirmed the scientists expectation that the provision of protein before a workout would work just as well, because - more than anything else - it is the availability (or should I say abundance?) of amino acids in the blood stream that is the main determined of post the actual fractional protein synthesis rate (FSR) after moderate  volume workout like the one the participants conducted in the study at hand. In addition it did, at least as far as the protein synthetic response goes, neither make a significant difference, whether the subjects had all their protion at once before the workout or consumed it in 15min intervals before and during the workout.

Bolus or pulse = fast or slow? Pulsed whey does not equal casein (imho)

What I am personally not happy with, though, is the way Burke et al. equate the "pulse" protocol to the ingestion of a "slow" protein source, such as a micellar casein protein, for example. While they put that into perspective in the discussion of the results (see below) and despite the fact that do see the rationale of Burke et al. not to use a real slow digesting protein like casein in order to have absolutely identical amino acid compositions and to exclude other confounding factors, it is at least in my humble opinion somewhat confusing for the "average" reader. And while it is likely that the results for a "real" slow digesting protein would be similar, this would warrant direct experimental evidence. A fact the authors only hint at indirectly towards the end of the discussion of their results, when they state:

"[...] A specific issue in interpreting the finding of these previous studies and in increasing the utility of the concept of ‘‘fast’’ and ‘‘slow’’ dietary proteins is the difficulty of determining the individual and interactive contributions of the different AA composition of protein-rich foods and the digestibility of proteins or protein-rich meals to the pattern of delivery of these AAs. Our protocol, in which the same (fast) protein was consumed to achieve its traditional AA profile or as a series of small divided feed-ings to replicate the plasma leucine response associated with a slow protein, provides an opportunity to differ-entiate these effects." (Burke. 2012)

But hey, who knows, maybe that's going to be the research question of the next paper... and in the mean time it will spare you to buy two or even more different protein powders ;-)

"So what's better Dr. Andro? Pre- or post-workout protein supplementation?"

I guess most of you won't care anyways, as there is another question that's now preying on your minds... but to be honest, I can't provide you with a definite answer to it (see headline). What I can do, however is compare the study by West et al. (West. 2011) which used 25g of whey protein post workout to the one at hand (Burke. 2012).

Figure 2: Fractional protein synthesis (FSR in %/h) after the workout with post workout protein ingestion (West. 2011) and pre workout protein ingestion (Burke. 2012) on the left; relative increase in FSR in the two trials (compared to fasted for West. 2011 vs. Placebo for Burke. 2012) on the right (please mind that this is by no means a scientifically valid comparison, it's more of a "food for thought illustration"!)

I've done just that for you in figure 2, and what this comparison tells you is that it does not make a difference, whether you ingest all your protein as a bolus after a workout or start "pulse ingesting" (mind my words in the previous paragraph wrt to "slow != pulse") your protein 45min before the workout - at least, if you take the relative increase in fractional protein synthesis as a measure (figure 2, right). 

Unfortunately, both the composition of the protein supplement (25g whey in West. 2011 vs. 25g whey + 5g leucine in Burke. 2012), as well as the exact outcome variables that were measured (1-3h and 3-5h FSR in West. 2011 vs. 5h post workout FSR in Burke. 2012) were different, so that the comparison of the relative increases in protein synthesis I plotted on the right hand side of figure 2 is actually not 100% valid.

Moreover, and this is something I know a couple of you will now be thinking of, this comparison does by no means allow for any quantitative predictions with respect to the question of ...

What would happen, when you do both: Pulse ingest before and bolus ingest afterwards?

If  you don't remember or - even worse ! - have not read the previous SuppVersity post "Protein Synthesis Beyond the '20g Limit': Study Shows Exercise Facilitates 32% Greater Increases in Fractional Protein Synthesis With 40g Instead of 20g of Whey PWO" click on the image and (re-)read it ;-)

In view of the fact that the existence of a "threshold level" of protein intake, where the addition of even more protein won't yield any further benefits appears to be self-evident, the exact amount of this limit has yet still to be determined. At least after a workout, it seems that this threshold would be higher than the 25g and 20g of protein the subjects ingested in the Burke and West studies, respectively (please read my previous post "Protein Synthesis Beyond the 20g Limit" for a more detailed discussion of this topic).

That being said, it is reasonable to assume, but would likewise warrant experimental verification, that the combination of both protocols could increase the fractional protein synthesis even further. Yet while I am 100% sure that they won't simply add up, I would hesitate to bet money that the difference would actually reach statistical significant... at least with a low volume leg extension workout as it was used in the studies at hand.

References:

• Burke LM, Hawley JA, Ross ML, Moore DR, Phillips SM, Slater GR, Stellingwerff T, Tipton KD, Garnham AP, Coffey VG. Preexercise aminoacidemia and muscle protein synthesis after resistance exercise. Med Sci Sports Exerc. 2012 Oct;44(10):1968-77.
• West DW, Burd NA, Coffey VG, et al. Rapid aminoacidemia enhances protein synthesis and anabolic intramuscular signal-ling responses after resistance exercise. Am J Clin Nutr. 2011; 94:795–803. 
• West DW, Phillips SM. Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training. Eur J Appl Physiol. 2012 Jul;112(7):2693-702.