MacNaughton et. al. The response of muscle protein synthesis following whole-body resistance exercise is greater following 40 g than 20 g of ingested whey protein. hysiol Rep, 4 (15), 2016, e12893
The currently accepted amount of protein required to achieve maximal stimulation of myofibrillar protein synthesis (MPS) following resistance exercise is 20–25 g. However, the influence of lean body mass (LBM) on the response of MPS to protein ingestion is unclear. Our aim was to assess the influence of LBM, both total and the amount activated during exercise, on the maximal response of MPS to ingestion of 20 or 40 g of whey protein following a bout of whole-body resistance exercise. Resistance-trained males were assigned to a group with lower LBM (≤65 kg; LLBM n = 15) or higher LBM (≥70 kg; HLBM n = 15) and participated in two trials in random order. MPS was measured with the infusion of 13C6-phenylalanine tracer and collection of muscle biopsies following ingestion of either 20 or 40 g protein during recovery from a single bout of whole-body resistance exercise. A similar response of MPS during exercise recovery was observed between LBM groups following protein ingestion (20 g – LLBM: 0.048 ± 0.018%·h−1; HLBM: 0.051 ± 0.014%·h−1; 40 g – LLBM: 0.059 ± 0.021%·h−1; HLBM: 0.059 ± 0.012%·h−1). Overall (groups combined), MPS was stimulated to a greater extent following ingestion of 40 g (0.059 ± 0.020%·h−1) compared with 20 g (0.049 ± 0.020%·h−1; P = 0.005) of protein. Our data indicate that ingestion of 40 g whey protein following whole-body resistance exercise stimulates a greater MPS response than 20 g in young resistance-trained men. However, with the current doses, the total amount of LBM does not seem to influence the response.
So first let me thank Brad Schoenfeld for making me aware of this paper. It’s quite timely given that I’m currently mired (yes, mired) in the around workout nutrition chapter of the woman’s book. Now, in recent years, the whole post-workout nutrition thing (or more generally around workout or peri-workout nutrition) has become a little bit more confusing than it was originally.
Back in the day everybody knew you had to consume carbs and fluids (endurance athlete) or carbs and protein (resistance training) for optimal results. If you didn’t consume it within an hour, you had failed as an athlete. The real bros believed in consuming your post-workout drink on the way out of the locker room. YOU DON’T KNOW THEIR WORK ETHIC.
Studies supported it, bros knew it, it was The Way ™, Dr. John Ivy wrote a couple of books about Nutrient Timing and I wrote an extended chapter in The Protein Book about it. Now, it’s a little less clear. The smug one, Alan Aragon wrote a review paper on the topic a few years back which made the point that the whole idea of a post-workout anabolic window might be less important than thought, at least for most situations.
He pointed out, rightly, that most studies were done fasted. While this isn’t unheard of, the situation changes completely if you’ve eaten within 4 hours of a workout. At least some work suggests that PRE-workout protein outperforms POST-workout protein anyhow. Even the fastest digesting protein takes a solid 30 minutes to release amino acids while a pre-workout protein source will be digesting when the workout ends. The bros should have been drinking their whey walking IN to the locker room instead of OUT. SOME WORK ETHIC.
Adding to this, even rapid glycogen refilling isn’t really that important under most circumstances. It takes a LOT of weight training to deplete muscle glycogen, 6-9 sets might deplete 40% and I calculated for UD2 that it takes 12 high-rep sets to deplete it by 75%. Yes, many do more work than this but when they do, it would be unlikely for them to do it frequently. The same goes for High-Intensity Interval Training. Yes, a single 30 second all out sprint can deplete glycogen by 25% in the legs and you can potentially deplete local muscle glycogen in a single workout. But almost nobody does them more than every few days (swimming might be an exception).
Even at the slowest rates, muscle glycogen (and glycogen is only used locally, depleting of the arms doesn’t impact on the legs) will refill within about 20 hours. So long as total carbohydrate goals are met, it’s just a non-issue for most situations. A situation where it absolutely matters is when athletes are performing exhausting training for the same muscle groups with less than 8 hours between them.
This doesn’t include most sports and certainly doesn’t include the general trainee. Even most major groups providing nutritional guidelines to athlete aren’t that focused anymore on post-workout recovery at least not in terms of having to maximally refill glycogen as rapidly as possible. Daily protein and carbohydrate targets are more important. There are other situations, when people train fasted or haven’t eaten for more than about 4 hours before training where post-workout is important. For most people, it just doesn’t matter that much.
Ignoring that, there is still interest in the topic, primarily in terms of what might be the optimal dose of protein to support muscle growth. For several years now, an idea has been floating around that anything more than 20-25 grams of protein has no impact on muscle protein synthesis (MPS). Please note that I said synthesis. There is also the issue of muscle protein breakdown (MPB) and it’s the combination of the two that determines that happens to muscle. One recent study found that more protein (70 grams vs. 40 grams) not only maximized protein synthesis but the larger amount decreased muscle protein breakdown. Unfortunately, it was looking at whole body protein breakdown and not skeletal muscle specifically.
And more unfortunately, there is actually very little research looking at muscle protein breakdown outside of one study suggesting that overall it has a fairly minimal effect (perhaps less than 30% of the total response). If you’re wondering why so little research has been done it’s because measuring MPB is technically a bitch. I also don’t happen to consider 30% to be insignificant and most of these studies are fairly short term (a few hours) which raises the question of whether changes in MPS or MPB occur later. Anyhow.
Now you might see another problem with the whole 20-25 grams of protein maximum value which is that it’s given in absolutes. It seems inconceivable that two lifters with different amounts of lean body mass (LBM) respond to identical amounts of protein. Smart folks put it in terms of body weight anyhow with a recommendation of 0.18-0.22 g/lb (0.3-0.5 g/kg). Which brings me to today’s paper which set out to address two questions.
The first was whether a larger amount of protein would increase MPS to a greater degree, the second was whether lifters with different amounts of LBM would see a differential response.
To this goal the researchers recruited 30 young males who were very recreational lifters and had been lifting at least two sessions per week for more than 6 months. While this is kind of a limitation, it might be seen as a strength in that less well trained lifters tend to show a greater response to training than more advanced people so any effects might be a bit more pronounced. They varied in weight and lean body mass with one group having ~60 kg (132 lbs) and the other 76 kg (167 lbs) lean body mass and this was the major difference (bodyfat percentage and such were the same).
On both test days the subjects were fed a standardized breakfast, waited 2 hours and were then infused with a radioactive tracer and all of the other boring technical stuff that was done. They waited one hour and performed a full body weight training workout consisting of chest press, pulldown, leg curl, leg press and leg extension. Leg work was done one leg at a time and they did 3 sets of 10 at 75% 1 repetition max followed by a fourth set to failure. Reps were done on a 1 second up, 2 seconds down cadence. The second workout was matched to the first and each group consumed either 20 or 40 grams of whey protein after a biopsy was taken and both groups did both amounts of protein with a 2 week washout. A second and third biopsy were taken 3 and 5 hours later at which point the study ended.
A whole host of stuff was measured including things like blood and intracellular amino acid concentrations, amino acid oxidation, phosphorylation of one of the important factors (p70S6K1 if you must know) involved in signalling muscle growth but the main one of relevance was a direct measurement of MPS.
The study made a few interesting observations. The first is that leucine appearance was slightly faster with the 20 grams whey dose versus the 40 gram whey dose with the peak occurring at 30 minutes versus 60 minutes. Not surprisingly, leucine levels were higher at all time points with the larger amount of protein. Also not surprisingly intracellular levels of leucine were higher with the larger amount of protein. Amino acid oxidation (burning of aminos for energy) was also higher with the higher dose but this too is not that surprising as amino acids in excess of what can be used tend to be burned for energy. Honestly, none of this is surprising since you would expect more protein to release more amino acids into the bloodstream and that this would transiently affect the amount in the muscle itself.
As one of the few interactions with body weight, the lower LBM group showed a larger phosphorylation of p70S6K1 than in the high LBM group. This makes some logical sense as a smaller individual would be expected to have a higher peak concentration of amino acids in response to a given amount of protein. Since it’s leucine that tends to drive the bus on this (via activation of mTOR) a higher peak leucine concentration would be expected to impact on this more.
Despite that, and contrary to their first hypothesis, the amount of protein given showed no interaction with LBM in terms of actual increases in MPS. Both the smaller and jackeder dudes had the same response. This seems contradictory to the changes in p70S6K1 phosphorylation. But there is the fact that often these little markers of growth or MPS don’t actually correspond with the measured increases. It’s why focusing on reductive pathways often misses the big picture. Who gives a damn what happens to p70S6K1 if MPS isn’t different?
But MPS was different, though in the opposite direction to phosphorylation of this marker which further supports it as not indicating much. While the difference wasn’t huge more protein did in fact stimulate more MPS. I’ve presented the results below. That is, more protein stimulated more protein synthesis following training. I’ve shown the results below.
The difference was statistically significant even if we might question the real world relevance of it.
Ok where to start with this? First and foremost, it’s interesting that both the smaller and jackeder guys got the same response to the different protein intakes. You would expect it to scale with the amount of LBM but it didn’t. This might be due to the fact that, as people often forget, muscle is only a portion of the body’s total LBM (water, glycogen, organs, brain, etc.). It’s only about 40% and maybe that made the differences in actual skeletal muscle small enough to not matter. Still, it’s a little counterintuitive. Perhaps a followup study would benefit from providing protein relative to LBM to see if scaling it that way gave a different result.
Of some interest was that more protein did in fact have a larger impact on protein synthesis which goes against the previous studies on this. There are a couple of possible reasons for this. One is different in study methodology. Part of this has to do with differences in the sources of protein used. The studies which found a maximal effect of 20-25 grams used egg protein, this study used whey. Differences in speed of digestion or amino acid profile could play a role here; we know that leucine is a key player in this and dairy proteins (and surprisingly pea protein) have the highest concentrations. Not a lot of comparative work has been done looking at different proteins (although dairy/whey proteins consistently outperform soy protein) and most use protein powders or isolates. Perhaps whole food would be different.
This adds to the fact that most studies of this sort tend measure things for relatively short periods of time, 3 or so hours. It’s possible that the digestion speed of different proteins will have a different longer term response. But it’s methodologically difficult and expensive to do these studies. This study did use a 5 hour measurement window and that might have had an impact on the differences seen if MPS is increasing more at a later time point.
Perhaps the biggest difference, and the one that the researchers think was mainly at work was differences in the training that was done. The first two studies on the topic used only leg training while this study used full-body training. It makes some logical sense that recruiting/activating growth in more total muscle would require more protein to maximally stimulate growth. That is, supporting growth for all muscles in the body should logically take more protein than in just the quads or arms or whatever. The researchers even state
We conclude that more protein is necessary for the increased stimulation of MPS following whole-body compared to unilateral or bilateral resistance exercise.
So what can we take from this study? I think it depends on your perspective. Clearly, at least when looking at a full body workout, more protein stimulated more protein synthesis. At the same time, the lower dose of protein clearly did most of the heavy lifting and generated most of the response. Doubling protein intake didn’t double the response and you could just as easily argue that “20 grams of protein is more efficient” as “40 grams of protein is superior”. Mind you, over time, small differences can add up but even here, we are looking at adding tiny amounts of protein to muscle from each workout. A 20% increase in MPS from double the protein intake is still miniscule in absolute terms. Of course, every bit counts. We also don’t know if there is a dose-response threshold. Maybe 25 grams works as well as 40. Or 30 grams. Or 37.2 grams. This compared two doses and you can’t conclude anything beyond that.
It’s still weird that there was no relationship between protein dose and total lean body mass. Chalk that up to the “I dunno” file for the time being since it makes no logical sense at a fundamental level.
A final comment, from a result I didn’t mention above. The researchers did find that, while more protein increased protein synthesis to a greater degree, the absolute measured response was still about 75% of the response seen in the earlier studies on leg training only. That is, training the full body led to a decreased response in MPS overall compared to leg training only. The researchers speculate that this is due to the ingested amino acids being more dispersed over the body to support the changes in all muscle groups.
Things That Make you Go Hmmmm
And this raises a handful of questions in my mind.
Would even more protein overcome this? That is, if you’re trying to support growth in more total muscle mass (and here I’m talking about more muscle groups, not a guy with slightly bigger biceps than another), would eating even more protein raise MPS in all those muscle groups to reach the same level. The body only has so much blood and one aspect of increased protein synthesis and nutrient delivery following training is increased blood flow. Perhaps the body simply can’t deliver nutrients to all worked muscles no matter wat you do.
But keeping in mind the fact that the absolute increase in MPS is tiny after any given workout to begin with (growth is a long-term response to training and is slow as paste), here are a few things that make you go hmm….
Is it possible that split routines are potentially superior for growth compared to full body routines due to the fact that less muscle mass is being activated so that post-workout or daily nutrition can better support growth in the trained muscle. That is, if you only train say, chest/back and get a 25% higher increase in MPS compared to training full body, will that be superior for growth? Will it differ acutely versus long-term (where eventually you’re reaching your genetic limits no matter what you d0)?
We know that people who specialize tend to show better short-term and overall responses than folks who don’t. Specialization bodypart routines allow better growth in the focus muscles, bench specialists outperform three lift powerlifters, triathletes underperform single sport runners, cyclists or swimmers and decathletes always perform less compared to guys who specialize in the single events. Is muscle growth similar?
Certainly some of this is just due to the fact that you can only put enough intense training into so many things at once. A runner only runs, a triathlete has to spread their training across three events (and many are starting to focus on a single event while maintaining the others to bring them up). But I’ve theorized that the body has limited adaptational capacities, you can only adapt so many things at once. And this study, very obliquely supports that. The protein synthesis response (which was only measured in the quads) was lower when the full body was trained compared to earlier studies that only used leg training.
The limited studies seem to suggest that overall growth isn’t different so long as volume is equated so maybe it doesn’t matter in the long-term. But it is something to think about, no?
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