A Scientific Guide To Protein Intake With Training: What to Eat, How Much and When
Author: Langer, Henning; D'Hulst, Gommaar
Date: 2020-11-04

A scientific guide to protein intake with training

What to eat, how much and when

Gommaar D'Hulst & Henning Langer

Health is the greatest of human blessings

- Hippocrates -

W ho are we? A quick look into the background of the authors.

Gommaar D’Hulst, PhD

Gommaar studied Sport Sciences and Exercise Physiology at the University of Leuven in Belgium where he also obtained his PhD. During his PhD he studied the molecular biology of the working skeletal muscle. Currently he is working at the state-of-the-art Laboratory of Exercise and Health at the ETH Zurich where his research focuses on topics like muscle health and muscle memory. Gommaar has always been very passionate about communicating evidence-based information to the public. In his spare time you can find him playing with his 2-year-old son or at CrossFit Kreis9 for his workout of the day.

Henning Langer, PhD (c)

Henning is a Postdoctoral Researcher in muscle physiology at the University of California, Davis. His work investigates skeletal muscle health and how it can be modulated through exercise and nutrition. He did his PhD at the Charité - Universitätsmedizin Berlin, focusing on changes of muscle metabolism in neuromuscular disorders. Previously, he obtained his MSc from Maastricht University for work on skeletal muscle protein turnover in response to protein ingestion and resistance exercise. Henning is a certified strength and conditioning and CrossFit Level-1 coach. He has competed as an individual and as part of a team in CrossFit European Throwdowns and Sanctionals, including the German- and the French Throwdown.

Table of contents

1.
Background

1.1.
Protein: the building blocks

1.2.
Muscle protein synthesis

1.3.
Muscle protein breakdown

1.4.
Net protein balance and changes in muscle size

1.5.
Why measure muscle protein turnover and not just muscle growth?

2.
Protein consumption to optimize adaptations to strength training

2.1.
How much protein after strength training works best?

2.2.
20 gram of protein: one-size-fits-all?

2.3.
Is there a difference between exercising one muscle group compared to the whole body when it comes to protein intake?

2.4.
Protein: how much per day?

3.
Protein quality: are all protein sources the same?

3.1.
What determines protein quality?

3.2.
Leucine - why is it so important? An introduction to the cell biology of MPS

3.3.
Is leucine alone enough to maximize mTOR, MPS and growth?

3.4.
Leucine availability in foods and its effect on total protein intake: Implications for plant-based proteins

3.5.
What about other macronutrients? Do carbohydrates and fat augment muscle protein synthesis?

4.
Protein timing

4.1.
The ‘anabolic window of opportunity’

5.
Protein Distribution

6.
Protein before bed

7.
Protein and ageing

8.
Protein and weight loss

9.
Protein and endurance exercise

10.
Conclusion

11.
Closing Remarks

12 .   Acknowledgements

1.    Background
1.1.        Protein: the building blocks
By Gommaar D’Hulst

You have heard some version of this a lot: “protein is essential to optimally recover from a hard workout”, or “protein helps to build muscle mass during periods of strength training” and “proteins are the ‘building blocks’ for your muscles”. But why is protein so important?

The proteins you eat are broken down into little chains of amino acids (peptides), which are eventually further broken down into single amino acids.

S keletal muscle accounts for approximately 40% of the body weight in humans, making it the largest organ by weight (skin covers more surface area, but weighs less). Healthy skeletal muscle is comprised of approximately 20% protein, making protein its main structural, functional and biochemical component. As protein itself is comprised of amino acids, it could be said that amino acids are the primary ‘building blocks’ of the human body. Indeed, the name itself already suggests its importance since “protein” is derived from the Greek word “prōtos”, meaning “first”.

All cells, including muscle fibers, are in a constant process of making new proteins (synthesis of new proteins) and breaking old, dysfunctional proteins down (breakdown of proteins). The balance of these processes are frequently used as ‘read-outs’ for the efficacy of various interventions (e.g. the source and timing of protein supplementation) in research studies.

These physiological processes are integral to skeletal muscle function and we want you to understand them particularly well, which is why we will start by digging a bit deeper into the fundamental biology underlying them.

1.2.        Muscle protein synthesis

By Henning Langer and Gommaar D’Hulst

By far the most commonly used method to directly measure de novo protein synthesis is through the use of stable isotope labelled ‘tracers’. The basic concept is to flag a certain metabolite so that you can follow its fate in the body. A commonly used contemporary method is “heavy water” labeling with deuterium oxide (D2 O). Heavy water is not dangerous and completely identical to regular water, with the important exception that it contains deuterium instead of hydrogen. Deuterium is an isotope of hydrogen that has an additional neutron, which causes D2 O to literally contain heavier atoms than regular water:

If somebody drinks heavy water, the main component of this water (i.e. deuterium) does everything that the components of regular water (i.e. “regular” hydrogen) would do. For example, a naturally occurring process is that certain amino acids can exchange one of their hydrogen atoms with circulating hydrogen. Alanine for example can replace up to four of its hydrogen atoms with “fresh” hydrogen. If alanine is exposed to deuterium, up to four of its hydrogen atoms can become replaced by deuterium. Since deuterium is heavier than regular hydrogen, alanine, which has incorporated deuterium into its molecular structure, is now heavier than regular alanine. This difference in molecular weight of alanine can be measured by different mass spectrometry techniques.

Like many other circulating amino acids, alanine is taken up by skeletal muscle and incorporated into newly made contractile proteins (i.e. de novo myofibrillar protein synthesis). By ingesting heavy water and labeling alanine in the circulation, we can “trace” the fate of alanine in different tissues. Imagine the following scenario:

Somebody drinks heavy water and his or her circulating alanine molecules become “labeled” with deuterium. If we now take two muscle tissue samples (“biopsies”) with two hours of time between them, we are able to tell how much new alanine got incorporated into the muscle samples by measuring how much heavier alanine in the muscle sample became over this time frame. If we also collect blood samples at the same time, we are then able to calculate how much heavier alanine became in the blood over those two hours. By comparing the rate at which alanine became heavier in the blood with the rate at which it became heav ier in muscle, we are then able to calculate the “fractional synthetic rate” (FSR) of proteins. There are different fractions in skeletal muscle (for example collagen or mitochondrial) and you will find different types of FSR measured in different papers, but for the purpose of this eBook we are referring to the de novo synthesis of contractile proteins, called “myofibrillar protein synthesis”. Whenever we mention MPS or FSR, we are referring to myofibrillar protein synthesis unless stated otherwise.

W hat we outlined abo ve is an oversimplification of a complex methodology, but it provides a fair representation of the general principle. Stable isotope labeling or tracing can be applied in a wide range of ways. Heavy water is just an example of a contemporary and convenient method to achieve the labeling of metabolites of interest. Stable isotope labeling can be applied to amino acids and protein turnover, but also to carbohydrate or fat metabolism.

Another historically popular method to investigate protein metabolism besides heavy water is the use of amino acids that have already been stable isotope labeled (such as leucine or phenylalanine). The principle is the same: the stable isotope labeled - and thus heavier - amino acids are infused into a subject, blood and biopsy samples are taken at various time points and the incorporation of the labeled amino acids into muscle tissue are calculated in order to determine rates of myofibrillar protein synthesis.

Leading experts on skeletal muscle protein at Maastricht University have taken this method to the next level: They have infused a dairy cow with stable isotop e labeled ami no acids (
Burd, 2013 ). W hy w o uld anybody bother to infuse a cow with labeled amino acids that are worth several thousand dollars? Well, if you milk the cow, then the protein in that milk contains a certain amount of stable isotope labeled amino acids. If you now serve that milk (or its protein isolates whey and casein), you are able to trace the exact fate of that milk in the subjects that ingested it. Cool stuff, isn’t it? You are what you eat, literally, and we can measure the rate at which that happens.

Here is another fun fact: baseline FSR numbers are usually in the range of ~0.035-0.050 % per hour. In other words, in one hour your body remodels up to 0.05 % of your muscle’s protein mass. In 24 hours that accumulates to 1-2 %. To quote Professor Luc van Loon, group leader of the renown protein laboratory in Maastricht mentioned above: “Now look at your right arm: in three months, every single protein in that arm will have been replaced. You will have an entirely new arm.”

This is a brilliant way to illustrate how plastic muscle tissue is and what a dynamic process protein turnover can be. If you want to learn more about muscle protein synthesis and the different techniques to measure it, have a look at this easily digestible summary by Dr Jorn Trommelen here
.

1.3.        Muscle protein breakdown

By Henning Langer

Changes in muscle size are of course not only governed by the building of contractile proteins (i.e. muscle protein synthesis; MPS), but also by their removal called “muscle protein breakdown” (MPB). The balance between MPS and MPB is the “muscle protein net balance” and determines whether a muscle eventually shrinks or grows. We will address the net balance more thoroughly in the next chapter.

MPB is comprised of several complex processes such as the ubiquitin proteasome system and autophagy. We know that there are numerous interventions that trigger these processes; for example, starvation, low protein intake, inactivity and immobilization or nerve damage will all initiate MPB. Somewhat paradoxically, overfeeding, high protein intake, physical activity and exercise also cause an increase in MPB along with a concomitant increase MPS. As such, since they increase both MPS and MPB, you could more accurately say that all the interventions mentioned above cause an increase in “muscle remodeling” rather than simply a plain increase in muscle size. This is an important concept to remember when we talk about MPS. Without also looking at the effect on MPB, we can’t really tell the potential for changes in muscle size of a certain intervention.

This is where things become problematic, though. While we have fairly robust techniques to assess indirect markers of MPB, directly measuring it is notoriously difficult. Often, indirect markers do not always correlate very reliably with actual changes. We will discuss this issue in respect to MPS a bit more thoroughly later in this book. The lack of reliable biomarkers for MPS is not as devastating, since we can still directly measure MPS itself through stable isotope labeling. MPB on the other hand is more challenging.

The main problem relates back to Figure 4 above and the nature of stable isotope tracing. MPS is calculated by measuring the rate at which labelled molecules from the circulation get incorporated into skeletal muscle. That is possible because you can isolate the contractile protein fraction in muscle samples. But MPB is about how fast amino acids get removed from this very protein fraction. We just learned that completely turning over all myofibrillar protein takes a couple of days. So until the labeled amino acids get removed from myofibrillar protein again, multiple hours (more likely days to weeks) will pass. And even if you waited that long, you are still left with a major problem: if amino acids are removed from myofibrillar protein by MPB and eventually leave the muscle back into circulation, how do you distinguish the origin of these amino acids? Amino acids that are newly labelled in the circulation, amino acids that were already labelled a while ago and have just recently been released by the liver, amino acids that got incorporated into muscle and were subsequently released again – they all weigh the same and are difficult to distinguish via mass spectrometry.

The aforementioned problem of having difficulties distinguishing the origin of amino acids is what the most popular method of measuring MPB troubleshoots to its advantage. It does so by quantifying the difference in amino acid composition between the arterial and venous circulation. The “Arterial-Venous” [A-V] balance is acquired by inserting catheters not only into a vein (veins are the vessels leading blood from your tissues and organs to the heart and are most commonly used to sample blood), but also into an artery (arteries lead blood from the heart to the periphery. They are usually situated much deeper within your body). The assumption is that the rate of appearance of labeled amino acids in the venous blood could only be a product of tissue breakdown, while the rate of disappearance of labelled amino acids from the arterial blood would represent tissue synthesis:

However, if the rate of appearance of labeled amino acids in the blood is your only measure of tissue breakdown, you still have no guarantee that these amino acids stem from muscle and not from other tissues (bone, skin, other muscle groups) in proximity to the vein. In addition, for the calculation of a rate of appearance in the venous pool you rely heavily on the measurement of blood flow via ultrasound, which is a challenging way to produce reliable data.

All this has led to a relative scarcity of MPB data compared to MPS data. Several experts in the field are of the opinion, however, that for most scenarios in healthy humans this does not pose a big problem. They hypothesize that changes in MPS are still suitable to predict changes in muscle size, because MPB is supposedly fairly stable, unless a stark, catabolic stimulus (such as immobilization or nerve damage) is incurred . However, a study in young men after resistance exercise found that, indeed, acute changes in MPS correlate only poorly with long term changes in muscle volume:

Some of the subjects with the lowest MPS response had great gains after 16 weeks of training. Conversely, some of the subjects with very high MPS rates at the beginning of the intervention grew relatively little new muscle. This could mean either of two things: either MPS is unreliable at predicting changes in muscle size, or MPS following a training session that involves unfamiliar/novel exercises is more indicative of muscle damage, remodeling and familiarization with exercise. What the latter means is that in situations where a subject is unfamiliar with intense resistance exercise and is then exposed to it, muscle takes disproportional damage (so-called "delayed on muscle soreness"; DOMS) that causes uncharacteristically high increases in MPS to help remodel the damage. However, these steep increases in MPS are also accompanied by similarly high increases of MPB, so that they do not result in net muscle gains, but instead repaired muscle tissue. From a practical point of view, it does not seem too farfetched to think that this could be the case: most of us have experienced how disproportionally strong DOMS can be if you are unfamiliar with an exercise, the intensity at which it is performed or the volume of work performed.

A recent study (Damas, 2016)
looked at this phenomenon and found support for the hypothesis. MPS was measured during the first week of training (T1), the third week (T2) and the tenth week (T3). The investigators also measured muscle size and muscle damage at all three time points. What they found is that there is substantially more muscle damage after training during the first week of training. As such MPS is particularly high, however, this MPS value correlates only poorly with the actual changes in muscle size at ten weeks. On the contrary, muscle damage is already reduced at three weeks and MPS values start to correlate fairly well with changes in muscle size. At ten weeks, when muscle damage is almost entirely absent, the MPS values correlate almost perfectly with the changes in muscle size in a subject.

S o what is the main take away from this chapter? First, we would like our readers to understand that human biology is complex and our methods to investigate it are imperfect. That does not mean they are useless, though. We have to be aware of their limitations and create suitable scenarios for them to be valid tools to precisely answer our questions. Second, while for the remainder of the book we will predominantly focus on MPS and the regulation of it after exercise and in response to nutrition, we wanted to acknowledge the role of MPB in skeletal muscle. Finally, we would like you to remain critical of the data we present. We will try to guide you through the evidence in a manner that allows you to draw applied conclusions, but we hope that the caveats of the methodologies stay present in the back of your mind. Ideally this awareness creates an opening for new or more precise data in the future that might or might not contradict some of what we describe here.

1.4.        Net protein balance and changes in muscle size

By Henning Langer

Now that the basics principles of MPS and MPB have been covered, we can start to introduce the concept of “net protein balance”. MPS and MPB are processes that are constantly fluctuating throughout the day. As we mentioned earlier, MPS is heavily influenced by what you eat and whether you worked out or not. For example, imagine you had a good training in the fasted state and subsequently your MPS and MPB were measured. That’s exactly what this classic study did:

As you would expect, resistance exercise increases muscle remodeling and causes MPS to be increased. However, you can also see that resistance exercise increases MPB, too. As alluded to in the previous chapter, this means that rather than causing muscle growth, the scenario described above is a situation where we have increased muscle protein turnover- basically the replacement of old (or damaged) protein with new protein without increasing the net amount of protein. We call this the muscle “net protein balance”. The math behind it is simple: If MPS exceeds MPB, the net protein balance is positive (i.e. protein accrual occurs and the result is muscle growth). If MPB exceeds MPS, the net protein balance is negative and muscle mass is lost. Indeed, the study above found that when net protein balance was calculated from the values above, net protein balance after resistance exercise was negative:

It might be a little surprising that the net protein balance following a powerful anabolic stimulus such as resistance exercise is negative, but it illustrates two things: First, it reemphasizes that MPS alone is more an indicator of remodeling than growth per se and only under chronic circumstances or in combination with an assessment of MPB can we truly make predictions for changes in muscle size based on it. Second, nutrition, and - as we will learn in the following chapters - protein ingestion in particular, are powerful tools to modulate muscle protein net balance, too. This was elegantly demonstrated in a follow-up study in which participants were given different amino acid mixtures, rather than being in the fasted state. They found that if resistance exercise is combined with the ingestion of mixed (MAA) or essential amino acids (EAA), net protein balance becomes positive:

As you can see, resistance exercise in a fasted state is again increasing MPS and MPB, but since MPB slightly exceeds MPS, net protein balance becomes slightly negative. However, if subjects received either MAA or EAA after resistance exercise, not only was MPS further increased compared to the fasted state, but EAA also appeared to have a suppressing effect on MPB. Most importantly, the combination of resistance exercise plus MAA or EAA resulted in a net positive balance, while resistance exercise alone did not.

What this shows is even though certain interventions such as resistance exercise are independently able to increase MPS, if the body isn’t supplied with the necessary building blocks it is unable to accrue any muscle protein and eventually muscle size. This is not to say nutrition is more important than training (most likely it is not), but it is definitely indispensable.

It is worth mentioning here that the reason they used MAA and EAA in the study above was not because they are more efficient than complete proteins in respect to their effect on MPS - it was purely related to the design of the study. In fact, we will provide detailed information on why a complete protein is superior to any isolated amino acid or amino acid combinations (i.e. BCAAs) when it comes to increasing MPS (chapter 3.3).

Furthermore, it is important to note that the decrease in MPB observed above is likely more related to the state of fasting and the break of fasting than a specific effect of EAA on suppressing MPB per se:

One of the conclusions from the study above (Figure 10) was that EAA could be powerful at suppressing MPB by “sparing” muscle tissue. The authors interpreted their data by hypothesizing that muscle tissue itself under fasting conditions is the primary source for EAAs in case the body needs them for replacing damaged muscle proteins (for example after resistance exercise). However, more recent studies have shown that relatively small amounts of insulin are already sufficient  to fully suppress MPB (Greenhaff, 2008 ). This makes the effects of EAA on MPB more likely related to the fact that they are mildly “insulinogenic”, meaning they cause a mild insulin release and break the fasting, rather than a direct signaling effect on protein breakdown. A similarly MPB suppressing effect can likely be achieved by the simple ingestion of carbohydrates.

In other words, while amino acids (preferably through a complete protein) after exercise are important to facilitate a positive net protein balance, their main effect is to increase MPS, while the ingestion of almost anything will result in a suppression of MPB.

As mentioned in the introduction of this chapter, MPS and MPB are processes that fluctuate throughout the day. Both are impacted by physical activity and nutrition, but also factors such as age or biological sex. Another interesting variable is training status. In response to a stimulus, untrained subjects have longer periods of elevated MPS compared to trained people. This fits nicely to the concept of ‘diminishing returns from training’. In essence, it means it is harder to gain muscle mass and strength for trained populations compared to untrained populations. Have a look at the following graph that nicely depicts the fluctuating MPS, MPB and protein balance over the course of a day . It is from a recent review paper (
Joanisse, 2020)
.

1.5.        Why measure muscle protein turnover and not just muscle growth?

By Henning Langer

Given the challenges associated with predicting changes in muscle size based on MPS and our limited ability to measure MPB, why not simply measure muscle growth directly?

The first important thing to acknowledge is that muscle protein turnover is not relevant only for assessing muscle growth. Indeed, while a lot of beginners are primarily interested in adding muscle mass to specific parts of their body, an athlete’s concern is usually directed towards performance. In fact, for most sports, including CrossFit, Olympic Weightlifting and Powerlifting, having as much strength, power and endurance while carrying as little mass as possible is advantageous. For those populations, protein intake as a tool to optimize recovery from a workout or, in other words, the remodeling of damaged muscle tissue, is more relevant than the idea of muscle growth. Therefore, muscle protein turnover or its proxy MPS are important readouts to assess the efficiency of certain food and exercise interventions.

Second, as mentioned in the chapters above, MPS does have some predictive value for muscle growth under certain circumstances. What is maybe even more important is that trials involving the measurement of MPS with stable isotopes are usually very tightly controlled. This means that all variables that could potentially alter the results, for example eating habits of the subjects, are standardized between the participants. The only variables unaccounted for are the genetics of the subjects (biological variability) and the reliability of the methods to measure MPS (any research technique comes with a certain margin of error). This is vastly different from training studies that measure muscle growth as their main outcome. While researchers try to control for lifestyle aspects such as eating habits as much as possible, the means available to them to do so (for example log books) are flawed and notoriously unreliable. Over the course of multiple weeks, this can have a significant impact on the final outcomes.

The challenge of biological variability between participants will always be present, irrespective of whether you look at an acute phenomenon like MPS a chronic phenomenon like muscle growth. However, excluding other variables such as the aforementioned lifestyle differences helps to increase your “power” to find differences between groups (if there are any). It is a matter of simple math (or, more precisely, statistics). Consider the following example:

The data from the figure above is from a seminal paper on protein ingestion after resistance exercise. The study tried to delineate how much protein you need after exercise to optimize MPS. Participants ingested either 0 g of protein, 5 g, 10 g, 20 g or 40 g. The study was conducted in people who had between 4 months and 8 years of training experience. Every subject participated in all five groups (0 g to 40 g), in a randomized order. They found that even consuming as little as 5 g of protein after training results in a significantly greater MPS than having no protein at all. 10 g appeared to have a slightly greater effect than 5 g, but the difference was not great enough to result in statistical significance. 20 g, however, had a substantially greater effect than not only 0 g, but also 5 g and 10 g. Finally, 40 g appeared to have a slightly greater effect than 20 g, but similar to the difference between 5 g and 10 g, the effect was not large enough to constitute a statistical difference. The conclusion of this study was that in recreational weightlifters, 20 g of high quality protein is the ideal dosage to optimize post workout muscle remodeling (MPS) and, potentially, could pave the way for improved muscle growth.

So how does this demonstrate the “power” of an experiment? They only needed to recruit 6 subjects to find all these effects. Despite a certain amount of biological variability between the subjects, the effect size was great enough and the methods precise enough to detect all those statistical differences. The best thing about it is future studies confirmed those results and showed that for most athletes and workouts, about 20g of protein ingested following the workout are ideal to optimize MPS (we will cover the exceptions to this rule in a later chapter).

Now, let's contrast that with how most chronic training studies are designed and carried out.

Check out Figure 13. It is a forest plot from a meta
-analysis showing the results of multiple studies that looked at the effect of protein supplementation on muscle mass gains (in kilograms) following resistance training
(Cermak, 2012)
. Each individual study shows only a small effect, which was often not statistically significant, because the variation between subjects was large (indicated by the width of the horizontal error bars). Only when you take all the studies together does the average (indicated by the diamond shape at the bottom) show a significant effect of protein supplementation. The reason these individual studies failed to show any significant effect was due to some combination of differences in the study population and inability to effectively control for variables such as training volume, food intake, etc. When this happens, a meta-analysis is often required because it allows you to “pool” your subjects. By effectively increasing the number of participants, you can increase your “power” to detect important changes. However, this is obviously much less efficient than having a well-designed experiment.

A s we discussed above, looking at MPS and looking at muscle growth are not the same thing. It is possible that part of the reason why the effect of protein supplementation on muscle growth is smaller than expected is that we are simply measuring different things. In later chapters we will explain why it is indeed more likely to be one of those variables which you usually cannot control tightly in long-term studies (i.e. overall food intake), explaining the discrepancies between results from acute and long-term studies. Furthermore, it is still quite remarkable that every single one of the 22 studies included in the meta-analysis had substantially more subjects than the acute study above (12 to 91 subjects compared to 6 subjects in the acute study). Usually having more subjects should heavily impact your statistical “power” and allow you a greater ability to detect effects (if there are any). So even if the effects are inherently smaller, because muscle growth is not the same as muscle remodeling, it is still surprising that the greater number of subjects was not able to balance that out in some studies and a meta-analysis was required to determine that protein supplementation after resistance exercise does indeed have a positive effect on muscle growth.

The main takeaway from this is not supposed to be some form of false dichotomy. Both types of studies, acute ones that measure MPS and chronic ones that measure muscle growth, are important tools to answer specific types of questions. As far as the effect of certain nutritional interventions or training methods on muscle remodeling go, measuring MPS is certainly the preferable approach. If the main question is whether a certain supplement or training method indeed results in more muscle mass, there is no way around putting them to the test in long-term training studies.

In this book we will try to provide you with a blend of both acute and chronic studies. Whenever we try to explain more thoroughly why something works the way it does, we will most likely rely more on acute studies. The reason is the aforementioned fact that they are commonly more tightly controlled and allow for a more distinct observation of biological effects. For a small part in later chapters, we will even briefly dive into the molecular biology of muscle growth. However, we will also provide you with the results from training studies and meta analyses whenever we focus more on guidelines and recommendations for applied sports nutrition.

2.    Protein consumption to optimize adaptations in strength training

2.1.        How much protein after strength training works best?

By Gommaar D’Hulst

As discussed in the previous chapters, maximizing post-exercise muscle protein synthesis is essential to facilitate muscle remodeling and lean mass gains. It has hopefully become clear that protein ingestion and resistance training work synergistically to boost MPS.

So, how much protein do we have to eat to optimize the effect on MPS?

In the last chapter we briefly mentioned this classic study by Dr. Dan Moore from Dr. Stu Phillips' lab at McMaster University (Moore, 2009 ). We used it to illustrate how small sample sizes in acute studies that look at MPS are sufficient to detect significant changes in response to exercise. Compared to that, long term training studies with many more participants struggled to find effects of protein intake on muscle growth. The reason for that was that MPS is not always predictive of muscle growth and, more importantly, training studies involve a lot of variables that are difficult to control for (i.e. daily food intake outside of training).

However, just because the study by Dr. Moore was able to find an effect of graded protein intakes on MPS with a relatively small sample size of participants does not mean that it did not suffer from being underpowered itself to delineate certain effects. Let’s dive back in for a moment: Young healthy males were asked to do heavy bilateral leg-based strength work (leg presses, leg curls and knee extensions), after which they were given 0 g, 5 g, 10 g, 20 g or 40 g of fast absorbing high quality whole egg protein (we will discuss the question of what constitutes high quality in a later chapter). For the next four hours, protein synthesis was measured in the leg via the stable isotope tracer methods we introduced in earlier chapters.

What the results showed was quite beautiful. There was a fairly linear dose-response in muscle protein synthesis with increasing protein ingestion up to 20 g. It was only after 20 g that there appeared to be a plateau, indicating that ingesting 40 g did not further augment muscle protein synthesis.

What happens with the additional protein that was ingested, but did not contribute to greater MPS? Most likely it was oxidized (burned) as fuel, as suggested by the linear increase in leucine oxidation (which is a surrogate marker of whole body protein oxidation) with graded protein ingestion.

So overall, this study would suggest the following:

In males with a body weight of 80 - 85 kg, 20 g of high quality protein is optimal to maximize training adaptation after strength training.

2.2.      20 gram of protein: one-size-fits-all?

By Gommaar D’Hulst

The recommendation of 20 g of protein as being optimal comes with some limitations. The study above was conducted in only six volunteers with an average body weight of 86 kg. If you look closely, there is still a 10 % increase in MPS with the ingestion of 40 versus 20g of protein. This increase was not statistically significant, but as we learned in the previous chapters, this 10 % increase could become significant if you expanded the number of subjects and included more than six participants. Furthermore, a 10 % difference in elite sports can be very relevant, even if it is not statistically significant. This all begs for some more questions that needed to be answered:

- "Could intakes greater than 20 g of protein after training turn out to improve muscle protein synthesis if tested in larger cohorts?"

- "Are 20 g of protein ideal for both 55 kg and 120 kg athletes?"

To answer these questions, a recent review summarized all the studies that looked into post-exercise stimulation of MPS with the ingestion of differing amounts of a well-researched protein (i.e. whey) (Moore, 2019 ). Based on the summary of the findings of these studies (12 in total), the authors tried to come up with a protein recommendation that is relative to a person’s body weight. They suggest that the ideal amount of protein after exercise lies around 0.31 g / kg body weight. Since most subjects in the study mentioned above weighed 86 kg, this recommendation of 0.31 g / kg body weight would result in a slightly higher protein dose than 20 g.

Here is what this calculation looks like:

86 kg x 0.31 g / kg = 27 g

Therefore, the ideal dose to optimize MPS after training for a person weighing 86 kg actually appears to be 27 g of high quality protein rather than 20 g. Beyond that, any effects of additional protein appear to plateau and are likely going to be oxidized instead of incorporated into muscle.

Again, summarizing the results of multiple studies has the advantage that more subjects can be included in the statistical analysis, improving the omni-present problem of being underpowered. This enables us to then detect smaller (but potentially relevant) differences of interventions. In this case, the authors confirmed that there was a ‘bi-phasic’ (meaning first linear, then logarithmic) increase in MPS with graded protein ingestion after exercise, with a plateau occurring at 0.31 g protein/kg body weight. With this body weight normalized recommendation, an 80 kg person should have ~25 g after training, a 50 kg female ~15 g and Eddy Hall (164 kg) ~50 g.

Consume of 0.31 g / kg bodyweight of high-quality protein after strength work to optimize muscle remodeling.

2.3.        Is there a difference between exercising one muscle group compared to the whole body when it comes to protein intake?

By Gommaar D’Hulst

The findings above were derived from studies that used resistance training as a mode of exercise. There are obviously nearly unlimited ways to do resistance training. Are you using isolated exercises targeting specific muscles (leg extension to target the quadriceps muscle) or are you doing CrossFit training (whole body exercises at high intensities)? And should your protein intake be adjusted according to what exercise you are performing?

To look more closely at this, the 12 aforementioned studies were further analyzed to estimate the amount of muscle mass (in kg) that was actively used during the different resistance training protocols. For example, a person would use less muscle mass while doing 4 x 10 reps of leg extensions compared to when he/she does a CrossFit-style workout consisting of squats, pullups and thrusters.

Using these data, the rate of muscle protein synthesis of each study was plotted against relative protein intake per kg of active muscle. For instance.

Despite up to ∼10-fold differences in relative protein intakes between studies, there was no observable relationship with the stimulation of muscle protein synthesis:

This suggests the amount of muscle mass which was trained has relatively little bearing on post-exercise protein requirements and that these requirements appear more dependent on total body mass

2.4.        Protein: how much per day?

By Gommaar D’Hulst and Henning Langer

So far we have talked about the protein requirements after training. However, this is unlikely to be your only protein intake of the day. Even though intermittent fasting is very popular amongst athletes, most will eat more than one meal per day.

Thus, the following questions need to be answered:

- "What role does total protein intake per day play for gains in lean mass with resistance training exercise?"

- "Is there an upper limit for daily protein intake after which the effects wear off?"

To answer these questions, let’s take look at a recent summary of multiple studies on the subject. In contrast to the previous paragraphs, where we discussed the effects of protein intake on MPS, this meta-analysis focused on studies examining changes in lean mass and strength after long term training. Combining 49 studies and 1863 participants, the data showed that gains in fat free mass started to level off beyond ~1.62 g protein per kg of bodyweight per day (Morton, 2017 ). At this point, the supplementation of protein after training had no additional effects on muscle growth and strength. In other words, if you eat a sufficient amount of protein (i.e. >1.6 g per kg bodyweight) over the course of the day, ingesting additional protein immediately after training is likely not very relevant for muscle growth (Figure 17). However, as we learned in the previous chapters, changes in muscle mass and changes in MPS are not synonymous with each other. This means that even though protein supplementation after training plays a smaller role for changes in size with sufficient daily intake, there could still be an advantage in terms of muscle remodeling. As such, it could still be relevant for those who are more concerned about recovery for the next training session to make sure that they have a timely intake of protein after training. We will address timing and distribution in a later chapter.

In summary, beyond 1.62 g / kg protein per day protein supplementation has no further effects on muscle mass and strength gains with resistance training.

Ergo: You should eat 1.63 g / kg of protein a day, evenly distributed in portions of 0.25-0.35 g/kg. How much is that in real food? Here are some exam ples:

- Average male (85 kg) active person: 140 g or 4.9 oz protein

- Average female (60 kg) active person (100 g or 3.5 oz protein

T he following table shows roughly the equivalent of (raw) food equivalent to 140 g (4.93 oz) and 100 g (3.52 oz) protein:

Food

Protein per 100g

Total (g) for 140g protein

Total (oz) for 4.9 oz protein

Total (g) for 100g protein

Total (oz) for 3.5 oz protein

Salmon

20.0

700

24.7

500

18

Tofu

12.0

1166

41

833

30

Greek yoghurt

4.8

2917

102

2083

74

Cheese

25.0

560

20

400

14

Milk

3.7

3784

134

2703

95

Peanut butter

26.0

539

19

385

14

Tomato

1.5

9333

329

6667

235

Steak

20.0

700

25

500

18

Here is how this could look like distributed over three big meals:

Breakfast

Lunch

Dinner

Oats
115/90g
(4/3.2oz)
Greek yoghurt
340/270g (12/9.5oz)

Rice
115/90g (4/3.2oz)
Veggie mix
230/180g (8/6.4oz)
Beef
230/180g (8/6.4oz)

Potatoes
340/270g (12/9.5oz)
Veggie mix
230/180g (8/6.4oz)
Tofu
370/300g (13/10.5oz)

You can see right away that these are relatively big portions of food. In case you are struggling with this, another option (more for practical reasons than data indicating an advantage) is to eat or drink high quality protein snacks such as protein bars, whey shakes or simply milk to comfortably reach your 1.6 g / kg protein goal by distributing your protein intake a bit more throughout the day.

3.    Protein quality: are all protein sources the same?

3.1.        What determines protein quality?

By Gommaar D’Hulst

Up until now we have talked about protein in general and as if all protein sources are identical. However, protein sources can differ immensely in amino acid composition, digestibility and other factors. There are two key criteria for determining ‘protein quality’:

- How many essential amino acids does the protein source provide?

- How well is the protein digested and absorbed?

There has been a lot of debate amongst researchers regarding what is the best method to determine protein quality. We will not go into too much detail here, but basically you have an older method called Protein Digestibility-Corrected Amino Acid Score (PDCAAS) and a newer method termed Digestible Indispensable Amino Acid Score (DIAAS).

PDCAAS for a food is calculated by comparing its amino acid composition against a reference pattern that roughly represents the nutritional needs of a human. The model of how they evaluated that is based on rat studies, which differ in many aspects of their metabolism from humans. An additional problem is that that the reference pattern is derived from a small group of children in the early 1980s who were recovering from malnutrition. Developmental growth and recovery from malnutrition make their needs difficult to compare to populations such as healthy adults or athletes.

DIAAS was developed to be an upgraded version of PDCAAS. It is based on a model developed in pigs (which are physiologically closer to humans than rats) and the scores of the different protein sources are not ‘truncated’ at a maximal value of 1. This allows to distinguish differences between higher quality proteins. For example, whey protein is 1.25, while soy is 0.98. With the PDCAAS model, these numbers would all be 1.

If you want to read-up more on both models, here is an easily digestible piece about it.

3.2.        Leucine - why is it so important? An introduction to the cell biology of MPS

By Gommaar D’Hulst and Henning Langer

Because of the challenges associated with the PDCAAS and DIASS methods, there are other, more straightforward ways to (roughly) assess protein quality. A lot of research indicates that the ‘quality’ of a protein source is to a large extent determined by the amount of the essential amino acid leucine present. In the following we will illustrate why that is.

Leucine is one of the three branched-chain amino acids (the well-known BCAAs). It is essential, meaning that it has to be consumed, because the human body cannot synthetize it. It is called ‘branched’ because of its aliphatic   side-chain  with a branch (a central  carbon  atom bound to three or more carbon atoms).

Higher quality plant proteins like soy commonly have 50-60% less leucine compared to animal proteins like milk proteins, meat, and eggs. A practical consequence of this is that ingesting identical amounts of plant protein compared to animal protein has been shown to result in lower rates of muscle protein synthesis after exercise:

You will find more details about the differences between plant-based and animal-based proteins in paragraph 3.4.

The phenomenon described above has led to the ‘leucine trigger’ hypothesis. According to this model, leucine is the key amino acid that triggers the rise in muscle protein synthesis after ingestion of a protein. Thus, proteins that are both richer in leucine and are ‘fast-absorbing’ (e.g. whey) would initiate a quick increase in leucine concentrations in the blood, which in turn stimulates the synthesis of new proteins. In contrast, a similar amount of low quality protein sources such as rice or potato protein would result in a much more modest increase in circulating leucine and subsequent synthesis. Intuitively, this would lead to the conclusion that proteins that are more slowly digested (e.g. casein) are unsuitable to efficiently increase MPS, as leucine enters the bloodstream relatively slowly. However, a lot of research has shown that slowly digestible proteins such as casein can still provide substantial increases in MPS (especially over time). Therefore, the rate at which a protein can be digested does not always predict MPS very accurately and the amino acid profile of a protein appears to be more important than the rate of appearance of its amino acids in the blood.

Nevertheless, it appears that leucine is a strong signal for the body  to initiate protein synthesis. If a protein source that has just been eaten is high in leucine, it is a green light to start the MPS machinery.

So, what is it about leucine that makes it such an important nutrient for muscle growth? Leucine is thought to stimulate MPS predominantly through a signaling molecule called ‘mechanistic target of rapamycin’ (mTOR).

To fully understand what we are talking about, we have to visit a little bit of cell biology history. In the early 1990’s three independent labs across the world discovered mTOR. It was found that when a specific compound produced by the bacterium
Streptomyces hygroscopicus
, known as ‘rapamycin’, was given to yeast cells, they stopped growing. Puzzled by the fact that only one specific compound could have such drastic effects on something as important as cell growth, researchers started screening for potential targets of rapamycin. In one of the screens, a large protein complex popped up to which rapamycin specifically bound. This protein was mTOR.

Fun fact: Rapamycin derived its name because the bacteria that produce it are exclusively found in the soil of Easter Island. Easter Island in native language is ‘Rapa Nui’.

Because of its strong immunosuppressive properties, rapamycin has been put forward as a potential ‘anti-aging’ drug. It fair to say that this molecule has become one of the most researched drugs in the world.

In the late 90’s, five years after the discovery of mTOR, muscle biologists discovered that activation of mTOR was strongly related to muscle growth. Through seminal experiments, researchers investigated how acute electrostimulation of skeletal muscle impacted mTOR levels (
Baar, 1999
). They found that muscles which showed the highest levels of mTOR activity after an acute stimulation were also the muscles that grew the most after six weeks of training, meaning that the increase in muscle mass correlated linearly with the acute activation of mTOR. Higher, acute mTOR activation led to more long-term growth:

Sidenote: Dr. Keith Baar, the first author of this 1999 paper, is the group leader of the laboratory Henning is currently working in. A whole new field of research emerged from the findings of this influential paper, which is summarized in the following figure.

F or a simplified overview, there are three types of external signals which regulate the initiation of MPS in skeletal muscle. Mechanical load (muscle contractions), amino acids (specifically leucine) and hormones (insulin, anabolic agents). Most signals have a specific way of turning on mTOR. They use different receptors and proteins (kinases) to convey their signal. Interestingly, these signaling cascades happen largely in parallel to each other. This means that heavy-load contractions can activate mTOR independent of protein ingestion or even insulin stimulation. Or, as data we discussed in earlier chapters indicate, when amino acids are ingested right before, during or after muscle contractions, both signals can potentiate each other resulting in increased MPS, decreased MPB and thus the potential for improved muscle remodeling and growth. All this is at least partially regulated through mTOR activity.

However, we also know that these signals (muscle contractions, amino acids, hormones) are of varying importance for muscle hypertrophy. For example, it is well known that ingesting protein alone will not maximize muscle growth without muscular contractions. Also there is data indicating that physiological hormone levels (testosterone, growth hormones, insulin like growth factor-1) following resistance exercise play almost no role in muscle growth compared to the impact of training or protein intake (
West, 2012)
. So, it is important to remember that even though many variables make an impact, they are not all equally important.

The same holds true for the role of mTOR: Does it govern everything and you just need some leucine-containing protein source after resistance training to turn it on? Unfortunately, no. The whole process of muscle growth is much more complex. There are very few absolutes in biology and we would like you to constantly keep that in the back of your mind with everything we discuss here.

In line with that, we would like to mention that aside from mTOR, there are quite a few other signaling proteins that play important roles in translating the external, anabolic signals mentioned above to increased MPS and muscle growth. We recommend reading these two excellent review papers by
Brad Schoenfeld
(
Schoenfeld, 2010
) and Marcus Bamman (Bamman, 2017
)
for more detail on that topic.

To further complicate things, there is data indicating that when you start a resistance training period, the initial activation of mTOR is much larger than what you find when you measure mTOR activity after a couple of weeks into the training (
Brook, 2015
):

In this study, one leg was exercised, while the other leg served as an unexercised control. R0 refers to the resting leg after the first training session, E0 to the exercised leg after the first training session. R3 to the resting leg after 3 weeks of training and so on.

This is somewhat similar to the phenomenon we discussed in chapter 1.4: the amplitude of MPS after the first onset of exercise is fairly different from what MPS looks like after a few weeks or multiple months of training. Therefore, the relationship between mTOR activation, MPS and muscle growth is not always linear and depends heavily on when you measure each process.

Finally, we also know that mTOR needs to be ‘in a range’ for the muscle to remain healthy. Both loss-of-function
(
Bentzinger, 2008
) and gain-of-function (Castets, 2013 ) models (where mTOR is severely decreased or over-activated, respectively) have shown to cause muscle deterioration, dystrophy and atrophy. Hence, spiking mTOR activation via exercise and protein intake is a good thing for muscle health, but chronic activation (as appears to be the case during aging) or chronic deactivation (sedentary people, low protein intake) seem detrimental to muscle health and should be avoided.

Now that we have discussed limitations and the complexity associated with mTOR, let’s refocus on its association with leucine and why leucine is thought to be an important indicator of protein quality.

To answer these questions, we are going to look at both in vitro studies (using only cells) and in vivo studies (using living organisms, in this case humans). The beauty of in vitro work is that you can investigate the interaction between specific molecules under very standardized circumstances, without interference of other variables such as genetic or lifestyle differences between study participants. The main drawback, however, is that the lack of these other factors simplifies the results to the point where they do not always reflect biology under living
(in vivo)
conditions.

Researchers have incubated skeletal muscle cells with different individual amino acids at high concentrations and subsequently assessed their effect on mTOR activation. Intriguingly, it was found that it was specifically leucine that increased the activation of p70s6k1, the main substrate for mTOR activity
(Deldicque, 2007)
. Other amino acids, such as arginine, isoleucine and other had no effect, while glutamine even decreased the activity of mTOR under those circumstances.

What you see in below is an analysis of a western blot assay. Western blot is a widely used technique in biology to visualize the quantity of a protein in a sample (you have already seen a western blot, two figures above this one). The stronger the intensity of a band, the higher the amount of that protein in a sample.

Based on these data you might be inclined to conclude that leucine would be the ultimate ‘go signal’ for muscle to initiate MPS. In line with that, muscle cells have been found to have specific receptor proteins that bind to leucine. These proteins can then signal leucine availability to mTOR. However, over the course of the last decade or so, other of such ‘amino acid sensors' have been discovered as well, for instance ‘sensors’ for arginine and methionine
(Wolfson, 2017)
. However, their role in muscle is still poorly understood and understudied.

But is leucine alone sufficient to optimize MPS and eventually growth, or are other amino acids necessary to potentiate the effects of leucine towards mTOR? It would seem the latter is true, if we were to infer it from the amino acid profile of most protein sources that are available in nature. Most of them contain leucine and 19 other amino acids, which may indicate that we need them, too.

3.3.        Is leucine alone enough to maximize mtor, MPS and growth?

By Gommaar D’Hulst and Henning Langer

In the last section we highlighted the importance of leucine for stimulating MPS, but ended with the question of whether leucine alone is enough or if a complement of other amino acids are necessary. Let us take a look at the results of an experiment that was recently performed Gomaar's lab. Muscle cells were incubated with an increasing dose of leucine ranging from very low (lower than the concentrations usually seen in the blood) to supraphysiological (much more than what is circulating in the blood under healthy conditions). In one condition only leucine was added to the cells (left panel), in the other condition, other amino acids were available in the medium in very low concentrations, too. The data demonstrates that the effects of leucine on mTOR are potentiated when there are other amino acids present:

You could use the metaphor of a mason who is supposed to build a wall. The mason gets a signal (i.e. leucine) from his boss to start building (i.e. MPS), but has to use bricks that are laying around on the floor from previous demolition works (i.e. amino acids that are broken down in the cell). This tedious work will most likely not result in a very high wall. However, when the mason receives help from other workers who bring him fresh bricks (amino acids from external sources like food),  he can work much faster and eventually build a high wall.

The concept of ‘leucine being the trigger, but other amino acids being required to fully potentiate protein synthesis’ was beautifully demonstrated by this classic study
(Churchward-Venne, 2012)
:

24 healthy, young adults went through an acute resistance exercise protocol and subsequently consumed one of three drinks: Either 25 g whey (hatched bars), 6 g whey with an additional dose of 2 g leucine (black bars), or 6 g of whey with an additional dose of every other essential amino acid except leucine (white bars). This means you had a group that consumed a complete protein at a dose that we know is likely close to optimal (hatched bars), a group that ingested less protein, but the same total amount of leucine (3 g) as the previous group (black bars), and a group that had less protein and leucine, but the same total amount of every other essential amino acid (white bars).

The goal was to see whether a suboptimal dose of a complete protein (6.25 g) could be “rescued” by simply ramping up the amount of leucine to match that of a higher protein dose. However, even though the effects on MPS at 1-3 h after resistance exercise were similar for all three groups, only the 25 g whey group had a prolonged increase in MPS (3-5h). This fits nicely with the idea that there is a certain amount of leucine required to trigger the initiation of MPS, but other amino acids are necessary to sustain it.

In summary: Mammalian target of rapamycin (mTOR) is a central governor of cell and muscle growth. The amino acid leucine independently activates mTOR and thus signals to the cell that it can initiate the synthesis of new proteins. To fully activate MPS, however, other amino acids are necessary as building blocks for creating new proteins. They also potentiate leucine’s signal towards mTOR via mechanisms we do not fully understand yet.

Want to learn more about the biology of mTOR? In case we sparked your interest, have a look at these mTOR series on YouTube by one of the discoverers of mTOR, David Sabatini, aka ‘mTOR-man’.

3.4.        Leucine availability in foods and its effect on total protein intake: Implications for plant-based proteins

By Henning Langer and Gommaar D’Hulst

After talking about leucine, mTOR and their potential effects on MPS and muscle remodeling, let us take a look at how this applies to real life scenarios and protein intake. For that purpose, we will take a look at proteins that commonly have a lower leucine content (plant-based proteins) and compare them with proteins that are known for being rich in leucine (animal proteins).

Plant-based proteins generally exhibit lower digestibility than animal-derived proteins. As briefly touched on in the previous chapters, this causes less of the dietary protein to be effectively digested and absorbed, resulting not only in slower, but also lower availability of amino acids in the blood stream. On top of this, plant-based proteins typically have 50-60 % less leucine per given volume than animal-derived protein sources.

Does this mean that plant-based proteins are to be avoided to maximize muscle remodeling after training? Not at all. You will just have to eat more.

Consider the results of this paper (Gorissen, 2016) :

Older adults were given 35 g of whey protein (a rapidly digested milk protein with plenty of leucine) or 60 g of hydrolyzed wheat protein (a plant protein, harder to digest and lower in leucine). 60 g of wheat protein was used to match the exact amount of leucine contained in the 35 g whey shake.

It turns out that the 60 g of wheat protein hydrolysate were equal to or even better at stimulating MPS than 35 g whey. Other studies have now replicated these findings, which suggest that the lack of quality of plant protein sources can be compensated by quantity.

Fun fact: Henning worked as a research assistant on this study during his MSc in Luc van Loon’s lab. One of the insights not directly reflected in the data was that ingesting 60 g of wheat protein was seriously challenging for many participants. So even though the wheat was able to match and slightly exceed the MPS response of whey, having to ingest such a high dose of plant protein in one sitting might come with certain practical limitations.

It’s fair to say that getting sufficient leucine from raw vegan protein sources can be challenging, because you have to consume a lot of it before you will reach the amounts recommended to optimize post-workout muscle remodeling ( ~2.5 g leucine). For instance, to get to the aforementioned amount of leucine by ingesting vegan foods that are relatively high in protein, you would have to eat 200 g of peanuts (roughly 1100 kcal) or 1 kg of spinach (not a lot of calories, but surely tough on the stomach). In contrast, you only need one serving (250 g) of Greek yoghurt to get your 2.5 g of leucine. A much more manageable dose.

Opting for vegan supplements can therefore be a good idea. The following paper summarized protein sources that are relatively high in leucine (van Vliet, 2015 ):

Protein powders of those plant-based food sources to the left of the figure can make life easier for vegan athletes who struggle to get their recommended protein intake (of sufficient quality) or vegetarian athletes who try to reduce their reliance on animal derived foods. In fact, a recent stud y has shown that whey and plant protein supplementation after training produce similar outcomes in measurements of body composition, muscle thickness, force production, WOD performance and strength following 8-weeks of CrossFit training (
Banaszek, 2019
). Previously, another study that compared adaptations to regular resistance exercise with whey or a plant based protein have found similar results (
Joy, 2013
). Hence, even though the common problems associated with the results of long-term training studies apply (see chapter 1.6) and even though there are certain challenges associated with it, the future of vegan protein supplements looks bright. However, as always, more research is needed.

To summarize this topic and to provide you with more guidance on your food choices to support training, we designed the following graph which depicts the amount of leucine per 100 g and 200 kcal of different foods.

3.5.        What about other macronutrients? Do carbohydrates and fat augment muscle protein synthesis?

By Henning Langer

We extensively discussed the amount and quality of your protein sources, but obviously we do not eat ‘only’ protein. Especially after a workout most people co-ingest some form of carbohydrates with their protein supplement and many natural protein sources inherently come with fat. Does this help or potentially hamper protein synthesis?

When you ingest carbohydrates, insulin concentrations in the blood rise because the pancreas starts to secrete insulin to keep blood glucose in narrow ranges. The amount of glucose in the blood is one of the most tightly regulated processes in the human body.

Let us rewind to the biological processes that regulate protein synthesis. It is well known that insulin alone and in sufficient dosages can robustly increase mTOR signaling and muscle protein synthesis in vitro (meaning in cell culture experiments) (Yoon, 2017 ). This happens independently of muscular contractions or amino acids. Intriguingly, the opposite in not true: findings in skeletal muscle cells indicate that amino acids can only stimulate mTOR and protein synthesis when there is insulin available (D'Hulst, 2020 ).

However, a review of clinical trials in humans found that when insulin is exogenously administered in physiological ranges in the absence of amino acids, MPS does not increase (Trommelen, 2015) . The reason appears to be that insulin itself causes hypoaminoacidemia (meaning a decrease of amino acid levels in the blood stream), which is a natural function of insulin shuttling nutrients into cells. This basically “cancels out” any directly stimulatory effects of insulin on MPS. If insulin is administered together with amino acids, MPS increases. However, that is an effect that can be attributed to the amino acids themselves, as we have discussed in chapter 1.5.

So, in this case, the in vitro data derived from cell culture experiments does not line up with the in vivo data from clinical trials in humans. The former showed that ‘insulin is required and sufficient for increased MPS to occur, independently of additional amino acid supply’. Whereas the latter showed the opposite, ‘amino acids are required and sufficient for increased MPS to occur, independently of additional insulin administration’. The reason can likely be found in the fact that cell culture experiments commonly use ~10 times higher dosages of insulin compared to what physiological concentrations in the human body are. Furthermore, no exogenously administered or otherwise derived insulin is necessary in vivo , because amino acids can indirectly (via gluconeogenesis) and directly (via “insulinogenic” amino acids such as leucine) stimulate a mild insulin secretion that is perfectly sufficient to permit a maximal increase in MPS. As touched on in chapter 1.5, this holds also true for the effect of amino acids on MPB. Only extreme, supraphysiological levels of insulin have shown to yield additional benefits for MPS and MPB. However, these levels cannot be achieved through nutritional means and require the abuse of performance enhancing drugs.

Therefore, to summarize, there is no need for carbohydrates in addition to protein to maximize MPS with and without training.

The fact that carbohydrates after training are not necessary to maximize MPS, however, does not mean you should avoid them after training. Carbohydrates do not hamper MPS either, as nicely demonstrated by a study that showed that carbohydrates delay protein absorption, but do not reduce MPS (Gorissen, 2014 ). Carbohydrates are essential to quickly replenish energy (glycogen) stores after exercise (ranging from endurance exercise to CrossFit and lifting weights). Unless you have a specific reason (such as weight loss), there is no compelling reason to avoid carbohydrates after training.

We will talk extensively about the use of carbohydrates and performance in our next book.

For the interaction between fat, mTOR and MPS, the data is a little more conflicting. The molecular data from cell culture and animal experiments suggests that a perpetually high fat intake is associated with an increase in mTOR activity in some types of tissue that is thought to contribute to insulin resistance via a negative feedback loop: Chronically elevated mTOR signaling is known to cause a decrease in insulin receptor substrate-1 levels (IRS1), thereby decreasing the ability of insulin to activate glucose transport into cells (Yoon, 2017 ). However, that does not appear to negatively affect survival in laboratory animals nor does it appear to impact all types of tissue equally. For example , skeletal muscle of animals that have been on a ketogenic diet for one month showed no substantial difference in mTOR activity (Roberts, 2017 ):

However, it is important to remember that for rodents to achieve a state of ‘ketosis’, not only do they have to exclude almost all carbohydrates from their diet, but also protein. The reason is that they are so efficient at gluconeogenesis that with even a moderate protein intake their body does not fully commit to ketosis. Irrespective of this, the Low Carb group in the mouse study above also did not change much in terms of mTOR activity. That is in line with the data from clinical trials in humans , which showed that co-ingestion of fat with protein does neither modulate amino acid absorption nor MPS (Gorissen, 2015 ):

Therefore, there is currently no evidence that an acute co-ingestion of fat or a short-term elevated fat intake would have detrimental effects on MPS, not even when study participants were already overweight and obese (Tsintzas, 2020 ).

As such, neither carbohydrates nor fat intake are likely to be anything worth worrying about in respect to optimizing MPS in humans.

4.    Protein timing

4.1.        The ‘anabolic window of opportunity’

By Henning Langer

“Eat your protein as soon as possible after your workout, or you will lose your gains” - an often heard recommendation in the gym that points to the existence of an ‘anabolic window of opportunity’. This implies that you have only a given amount of time in which you can optimally benefit from the synergistic effects of resistance exercise and protein supplementation.

Th e concept is based on older studies that found an increase in MPS with protein intake immediately after exercise compared to a later time point (Levenhagen, 2001 ), and studies that found improved gains in muscle mass with protein intake in close proximity to training compared to a later time point (Esmarck, 2001) . However, other studies could not replicate those results (Verdijk, 2008 ).

So until recently, the question remained:

Do the effects of resistance exercise and protein ingestion on MPS depend on each other?

The answer appears to be that they are largely independent from each other. This means that resistance exercise stimulates MPS, irrespective of protein ingestion and that protein ingestion stimulates MPS, irrespective of whether you have trained before or not. They still add up, so in a way they are synergistic, but you don’t need exercise to amplify the MPS response that you get from having your protein (and the other way around). Here is the data that allowed us to draw this conclusion (Wall, 2016) :

In this study, they exercised one leg of each subject  (unilateral leg press and leg extension until failure) and subsequently split all participants into two groups: Immediately following the training, one group received a drink of 20 g of carbohydrates (CON), the other group received a drink of 20 g whey protein (PRO). Before bed, the CON group received another 60 g of carbohydrates, the PRO group another 60 g of whey. The next morning, the MPS response of all subjects to 20 g of protein was tested.

If the muscles of the CON group were sensitized towards protein intake from exercise the day before (basically ‘yearning’ for the building bricks), while the muscles of the PRO group are already ‘full’ with amino acids, then the CON group should show a stronger response to the protein ingestion on the next day. However, you can see that all values between the CON and the PRO group are extremely similar to each other. MPS on the next day in the resting leg (i.e. the leg that was not exercised the previous evening) is the lowest (REST-FAST). There was no difference between the CON and the PRO group. The ingestion of 20 g of protein increased MPS in the rested leg by almost 100 % in both groups (REST-FED). The sub-conclusion of this is that protein ingestion increases MPS in an exercise-independent manner.

Looking at the exercised leg in the fasted state on the next day (EXERCISE-FAST), you find an increase of almost 100 % in MPS, too (so very similar to the non-exercised leg after protein ingestion). Again, CON and PRO did not differ. The sub-conclusion of this would be that exercise increases MPS in a protein-independent manner. Also, this means the effect of exercise on MPS is sustained independently from protein ingestion on the previous day . Finally, if we look at the MPS rates in the exercised leg after ingestion of 20 g of whey on the next day (EXERCISE-FED), everything comes together neatly: The individual values measured for protein ingestion (REST-FED) and exercise (EXERCISE-FAST) add up almost perfectly to a near 200 % increase in MPS.

Even though that was a study with a somewhat complex design (I had the pleasure to write my master thesis about it), it contains a vast amount of valuable data and a few important take-aways:

1. Exercise and protein ingestion stimulate MPS independently from each other.

2. The perpetual effect of exercise on MPS is sustained despite the complete absence of protein after training.

3. Protein ingestion on the previous day, after training, does not inhibit the MPS response to protein ingestion on the following day.

This is important, because it means that protein ingestion immediately following exercise is not crucial to reap the benefits of the training itself. However, since having protein immediately following exercise (and before sleep) also did not decrease the MPS response to a bolus of protein on the next day, having protein after training (and potentially before sleep) is still likely to speed up muscle remodeling.

Consider this: The study above only looked at MPS on the next day. We know and have illustrated in previous chapters (1.6, 2.1, 2.2), that MPS after training is further elevated with protein ingestion. This means that the PRO group above, which had protein immediately after training and before bed, definitely had higher MPS rates than the CON group on the previous day. So while MPS on the next day is not impacted by protein ingestion on the previous day, MPS on the previous day was.

In other words, even though protein ingestion after training is not time crucial, it likely still makes sense to have ample protein to optimize MPS and muscle remodeling. So, having your beef- or tofu - steak at home after training is just as good as your shake in the box, as long as you make sure you get it.

5.    Protein Distribution

By Gommaar D’Hulst

Pre- and Post-workout nutrition receive a lot of attention, but usually we eat food throughout day, not just one bolus right before or after training. So, can the way you distribute protein intake affect overall muscle protein synthesis throughout the day?

The answer appears to be yes, protein distribution does have an effect. In a well-executed study , young healthy males performed 4 x 10 RM leg extensions in the morning (Areta, 2013 ). After training their quads, they consumed 80 g of protein in a 12 h time-window throughout the remainder of the day. In one trial they consumed 40 g twice, one bolus right after exercise and another bolus 6 h later. In the second trial they distributed 20 g over 4 feeding periods. In the last trial they distributed 10 g over 8 feeding periods.

It turned out that 4 x 20 g was the best in terms of stimulating MPS over the 12 h measuring period.

This makes sense since we earlier explained that 20 g was roughly the dose which maximally stimulates acute MPS. 10 g is slightly too little and 40 g is likely too much with the surplus in amino acids being oxidized instead of incorporated into muscle tissue.

Nevertheless, some caution is appropriate here before drawing definitive conclusions from this study. The subjects only consumed whey protein throughout the 12 h the experiment and nothing else. This means they did not eat sufficient carbohydrates or fat to meet their total energy needs. It is also not a realistic scenario since most people eat a diet that balances all the major macronutrients. Results could potentially have been different when they were allowed to have other macros in addition to the protein. This is a lab-based study, future studies replicating real-life situations are needed to fully understand the importance of protein distribution. Regardless, the results from this study suggest that continued nutrition throughout the day is important for optimizing myofibrillar protein synthesis.

6.    Protein before bed

By Henning Langer

Now that we have talked about the window of opportunity and protein distribution, let’s take a look at another topic relating to these subjects: protein intake before sleep.

It’s a relatively common recommendation among laymen on the internet to ingest Greek yogurt or quark immediately before bed to increase muscle mass with resistance exercise. But what does the data say?

One of the first studies to look at this question was performed by Peter Res and co-workers in 2012 (Res, 2012 ). They recruited 15 young men and had them exercise late in the evening. After the exercise session, everybody consumed 20 g of whey protein and 60 g of carbohydrates. A few hours later, immediately before midnight, the subjects received another drink, this time either 40 g of casein or a protein-free placebo.

They measured MPS between midnight and the next morning and found that the group that received 40 g casein before bed had on average 22 % higher values:

This indicated that having a rather large amount of protein immediately before bed appears to be beneficial for muscle remodeling. To see whether the increased muscle remodeling would translate to greater gains in lean mass over time, the same research group conducted a randomized clinical trial . Led by Tim Snijders, the team found that protein before bed not only results in greater increases in muscle mass, but also strength (Snijders, 2015 ).

However, the results from this brilliant study were confounded by one crucial variable: total protein intake per day. Having the extra protein before bed caused the “Protein” group to ingest 1.9 g per kg body weight per day, while the “Placebo” group got 1.3 g per kg per day. As we already discussed in chapter 2.4, increasing the protein intake at least up to 1.6 g per kg per day seems to be beneficial for muscle mass, irrespective of timing of the intake.

Thus, while the data from the RCT was exciting and highlighted the potential of protein before bed, it is not clear whether it is specifically the timing or rather the sheer increase in protein ingestion per day that caused these results. To further complicate things, more recent data from the same lab has indicated that protein before bed does not result in meaningful increases in MPS if the amount of protein given before bed is 30 g as opposed to the aforementioned 40 g (Trommelen, 2018 ). Furthermore, when a similar clinical trial was conducted in older men, ingesting protein before bed did not result in additional gains in lean mass or strength (Holwerda, 2018) .

Therefore, it is fair to say that questions regarding protein before bed are still unanswered and need to be addressed before conclusive recommendations can be made. Have a look at this recent review for more information (Snijders, 2019) . However, based on the current literature it appears that, at least in young men, 40 g of protein before sleep could be an effective strategy to improve muscle remodeling as well as potentially muscle size and strength.

In the next chapter we will explain how protein requirements are affected by age and why it is particularly important to meet your goals if you are beyond a certain age.

7.    Protein and ageing

By Henning Langer

As mentioned in the previous chapter, there is data indicating the effects of protein on skeletal muscle might change with age.

One of the early papers on the subject was unable to find a difference in MPS of elderly and young people following protein ingestion (Symons, 2007 ). They tested the MPS of ten men around the age of 70 and ten men around the age of 40 after ingestion of 113 g of lean beef (yielding approximately 30 g of amino acids).

The result was that 40- and 70-year-old men responded similarly to this protein feeding:

However, as we learned previously, subtle differences in study designs can create big statistical differences, especially when it comes to sample size. A retroactive study by the M3 laboratory in Maastricht looked at what happens when you combine the data from multiple studies (not unlike a meta-analysis, but limited to a single laboratory) (Wall, 2015 ). What they found was that even though the dataset contained studies which, just like the one above, could not find a significant difference between young and old, once the data from multiple studies was combined, there was a significant difference between response to protein ingestion in young versus older men. Once again, what one study was not able to show, because the number of subjects relative to the effect size was not great enough, the synergy of multiple studies could. In this case combined data allowed researchers to compare 34 healthy young men (~22 years) to 72 older men (~75 years). As shown in Figure 40, while both young and older men had an increase in MPS in the post-prandial state, the effect was greater in young men. This emphasizes the effect that age can have on the efficacy of protein intake to stimulate MPS.

A very similar type of retroactive study from a laboratory at McMaster University in Canada had similar findings. Combining the data from multiple studies
, they showed a significant difference in how older versus younger muscle responds to protein intake (Moore, 2014 ). As a result they concluded that in order to optimize MPS and muscle remodeling, older subjects (in this study averagely 71 years old) need almost twice as much protein per lean body mass to achieve a similar effect to the ~0.3 g per kg recommended for younger athletes (see chapter 2.2 for more information).

There is no hard line after which you are suddenly old, but most literature above looked at participants >60 years of age. And while ageing is relative and some data indicate that the effects described above become less pronounced the fitter an older person is, increasing protein intake after training as you age appears to be a strategy that is supported by the literature.

8.    Protein and weight loss

By Henning Langer

Finally, let us address the role of protein intake during an energy deficit. Many protein related products are advertised with the promise of improved weight- and fat loss as well as muscle mass gains. In the following we will discuss in how far these claims are supported by the scientific literature.

The most comprehensive approach to get an overview is always to look at more than one study. For that purpose, let's take a look at a meta- analysis by Thomas Wycherley and colleagues (Wycherley, 2012 ). Through their literature search they found 1284 studies, out of which only 22 fit the tight inclusion criteria of their meta-analysis. The data from these 22 studies was extracted and analyzed for weight- and fat loss, as well as lean body mass. These were the results:

What you see above is a forest plot. It shows the weight loss results of every single study that was part of the meta-analysis for high and standard protein intake. The goal of this plot is to distinguish whether the sum of the data favors high protein intake for weight loss or standard protein intake. The red and black diamonds indicate the sum of the data. The black vertical line indicates “0” difference between high- and standard protein intake. Since you can see that the diamond is on the left side of the black vertical line, this means that the sum of the data found that a high protein intake is advantageous for weight loss.

You will ask yourself whether the same holds true for fat loss, as weight loss in itself does not distinguish between lost muscle tissue or burnt fat. Indeed, the same meta-analysis found that the effect for fat loss looked similar. People on a high protein diet usually lose more fat compared to those on a standard protein diet. So, if people on a high protein diet lose more weight, but also relatively more fat, what about lean mass?

The forest plot above shows the data of all studies within the same meta-analysis by Wycherley et al. but this time solved for fat free mass. As opposed to the forest plot for weight loss, this time the question is whether people on a standard protein diet or a high protein diet retained more fat free mass. The diamond on the right side of the black vertical line indicates that the sum of the data favors a high protein diet for the maintenance (or mild increase) in fat free mass.

Combined, these two forest plots indicate that a high protein diet favors general weight loss (in the form of fat mass) while preserving lean mass.

But how much protein constitutes a “high protein” diet during an energy deficit?

Amy Hector, who has conducted a number of studies on the subject as part of Stuart Phillip’s research group at McMaster, recently wrote a nice review on the subject
(Hector, 2018) . In it she concluded with a very easily digestible figure that conceptualizes the relationship between protein intake and energy deficit:

What she shows is that the greater the energy deficit is, the greater the protein intake should be to spare lean mass. As you shift the line to the right (e.g. are in at state of a greater energy deficit), a greater amount of your diet should come from protein in order to maintain lean mass. This appears to hold true until approximately a 35% energy deficit, after which more protein intake does not lead to improved lean mass retention anymore.

But what is the mechanism behind this? Why does higher protein intake help to save lean mass during dieting? The answer is relatively simple. Skeletal muscle tissue is the body’s greatest reservoir of readily accessible amino acids. During times of need the body can break down and recycle the amino acids from muscle to use them as building blocks of proteins in different tissues that are higher up in the hierarchy and need them urgently. Alternatively, amino acids broken down from muscle can then be utilized to make glucose (gluconeogenesis) for energy. Amino acids can also be converted to sugars via oxidative deamination and directly used as fuel by cells. All three processes are known to be increased in your body during an energy deficit.

Providing the body with a relatively higher protein intake helps to supply it with amino acids, ideally so that less muscle tissue has to be broken down to ensure adequate levels of amino acids in the body. However, this effect obviously has limits. During extended periods with great energy deficits and prolonged dieting, sooner or later a higher protein intake cannot compensate for the lack of energy provided by food intake and it will increase the breakdown of tissues other than fat and glycogen. This becomes more pronounced as the body’s fat reserves become smaller and less of the daily deficit is balanced by lipolysis.

That is why it is important to keep your energy deficit moderate (10 to 25 %), have a relatively high protein intake (1.5 g to 2 g per kg body weight, depending on whether you are on a 10 % or on a 25 % energy deficit), and try to keep the dieting fairly short. This strategy will put your body in a position where it will be able to maintain almost all its lean body mass while you decrease body fat and weight. Of course, if the loss of body fat is paramount for health or personal reasons, sacrificing a certain amount of lean mass is absolutely acceptable and should be expected.

That being said, with the recommendations above and a strict exercise regimen, it appears possible to even increase your lean mass a bit during a regular diet
(Longland, 2016 ):

In this study, a high protein intake (2.4 g per kg body weight) in fit college students resulted in a 1.2 kg increase in lean body mass, despite being on a 40 % energy deficit and losing 4.8 kg of fat. Meanwhile, the control group (1.2 g protein per kg body weight) could only maintain their lean mass and lost 3.7 kg of fat while on the same energy deficit. Dieting is really where protein intake starts to shine.

9.    Protein and endurance exercise

By Henning Langer

In the majority of previous chapters we talked about studies that evaluated protein intake after resistance exercise. We explained how much athletes should consume after lifting weights, over the course of the day, before bed, with ageing or during an energy deficit to enhance muscle remodeling or to facilitate gains in lean body mass. But what about other types of exercise? Do recommendations for endurance athletes differ from those for individuals predominantly engaging in resistance exercise?

A study published this year looked at the dose-response relationship between protein intake and muscle protein synthesis after endurance exercise (Churchward-Venne, 2020 ). Interestingly, they not only look at myofibrillar protein synthesis (the contractile protein fraction analyzed in most of the studies in this book), but also mitochondrial protein synthesis. Participants performed 90 min of continuous exercise on a bike at 60 % of their previously determined maximal power output (Wmax). Maximal power output is not equal to peak power output, but rather the last power output participants were able to maintain for at least 150 s during a graded exercise test. The participants in this study averaged ~5 W per kg body weight. This means for a 75 kg man, their Wmax in this study was approximately 375 W. This man would have had to perform 90 min of cycling at 60 % of 375 W, which equals 225 W. After the cycling all participants ingested 45 g of carbohydrates plus either 0 g, 15 g, 30 g or 45 g of milk protein. Myofibrillar- as well as mitochondrial protein synthesis were measured:

The data in the figure above indicates that while there is a neat increase in MPS with protein ingestion that continues up to 45 g of protein, 30 g is statistically sufficient to optimize myofibrillar protein synthesis following prolonged endurance exercise. For mitochondrial protein synthesis there appeared to be a similar pattern:

There was no statistically significant difference between just having carbohydrates and having carbohydrates with either 15 g, 30 g or 45 g of protein. Nevertheless, a p-value of 0.09 is fairly close to 0.05 (which is where commonly results are deemed significant) and could be called a “trend”. As such, while the effects of protein ingestion on mitochondrial protein synthesis remain unclear, the authors concluded that 30 g of protein are sufficient to stimulate myofibrillar protein synthesis in endurance trained men after endurance exercise. They also provided a breakpoint analysis of their data:

This shows that myofibrillar protein synthesis plateaus after subjects ingested ~0.5 g protein per kg body weight. Interestingly, that is substantially higher than the ~0.3 g protein per kg body weight we mentioned in chapter 2.2 for resistance exercise (Moore, 2019 ). The authors of the study in endurance athletes speculate that this increased need for protein to maximize myofibrillar protein synthesis could stem from increased breakdown of muscle tissue during endurance exercise (perhaps due to the duration of continuous exercise), increased oxidation of amino acids during endurance exercise as well as increased hepatic gluconeogenesis. Regardless, the reasons are not entirely clear and warrant further investigation.

In conclusion, it is fair to say that endurance exercise could potentially require more protein intake than previously thought. However, this statement largely concerns optimizing myofibrillar protein remodeling. Whether this translates to improved muscle regeneration with endurance exercise or even ultimately altered performance is unclear. Current recommendations for protein intake in endurance athletes range between 1.2 g and 2 g per kg body weight per day (Thomas, 2016) . This is very similar to the recommendations for resistance exercise mentioned in the previous chapters. Therefore, while there is still a lot that is not understood about protein recommendations for different types of exercise, current evidence suggests that they do not vary too much and that a daily intake between 1.2 g to 2 g per kg body weight is likely to cover the needs of most athletes in most situations.

Depending on the goals of the athlete and the period of training/competition they are in, protein intake can be shifted toward the lower (1.2 g per kg body weight) or higher end of the recommendations (2 g per kg body weight). The lower end allows for a higher intake of other macronutrients such as carbohydrates and fat and is likely to be beneficial at times where training volume is high and performance paramount. The higher end can be used when the athlete is either trying to lose weight while maintaining lean mass (see chapter 8) or when structural damage to the muscles of the athlete is expected to be high due to increased training intensities or work with unaccustomed types of exercises or exercise modes, known to provoke DOMS.

To optimize an athlete’s protein intake, personal preferences of the athlete and common food choices also have to be taken into account and accommodated as well as possible, to better ensure long term compliance.

10.   Conclusion

By Gommaar D’Hulst

There was a lot of info presented in this book, so we have summarized the most important findings for you here:

11.   Closing Remarks

People who have been following us for some time might  know that we are concerned about how scientific information is communicated to the general public. The rise of social media is great in many ways, but it is also a breeding ground for false information.

How scientific publishing is regulated in this world does not help either. Scientists design and conduct the experiments. When finished, the findings are interpreted and written-up in a scientific manuscript. To get the manuscript published, scientists send it out to a scientific journal and an editor will then decide whether it meets the journal’s scope and quality standards. If yes, he/she will send it to two or three so-called peer-reviewers, who are also scientists in the respective scientific field. They will then review the manuscript (without monetary compensation). Through this peer-review the manuscript gets accepted or rejected. In case of rejection, the scientist usually sends the manuscript to another journal and the process starts all over again. The article is accepted usually after some rounds of reviewing, in which the manuscript goes back and forth between scientists and more experiments to complement the data are conducted.

Finally, when a manuscript gets published, they are now readable for the scientific community. And this is where it gets gnarly: Most of the journals are access-restricted. This means that big institutes like universities pay thousands of dollars to get access to these journals in order for their scientists and doctors to be able to read the scientific literature. Who accounts for the biggest source of funding at public universities? The tax payer. And who has usually no access to all this information? Also the tax payer. You see, it is a strange system that does not make much sense from a business point of view for the public.

Long story short: It is very hard for the public to verify any of the information they receive every day, because they simply cannot read the scientific papers this info is based on. This of course does not make sense because it is the general public who pay the people who conduct the research. This is a particularly big problem in sport science and nutrition, because these are topics that are directly applicable for many people and are exceptionally prone to false information.

To help fight the system and get information to the public, we started @wod_science on various social media platforms. The goal, in our free time, is to distribute and communicate sport and nutrition science to the people who can benefit from it - not just the scientists, but the general public that hits the gym every day.

Luckily, efforts are made nowadays to change the system. Just recently, the University of California (the host academic institute of Henning) has canceled its subscription to Elsevier, one of the biggest scientific publishers. Manuscripts are uploaded to pre-print / bio archives (https://www.biorxiv.org/ , https://www.medrxiv.org/ , https://chemrxiv.org ), which have the advantage of being freely accessible to everyone, but have the disadvantage of not being peer-reviewed, which opens up more possibilities for bad science and even misconduct. Furthermore, many journals are now ‘open-access’,  which means that the scientists pay extra money for their manuscript to be published, with the reward that everyone can read it.

Finally, a Russian scientist named Alexandra Elbakyan has made a near complete database of all full texts of scientific studies that have ever been published in scientific journals. https://sci-hub.tw/ , while it is de facto the world's first open-access research library, is fought by the major publishing journals and as of now remains illegal.

12. Acknowledgements

Gommaar: This book would never been possible without the constant support of my beloved fiancée Evi. Evi, thanks for always listening to my nerdy science talk and for providing me the opportunity to put hours in this book while we have a small kid jumping around. Also, thanks for editing this book, without a ‘female eye’ the layout would have been a lot less appealing.

Henning: I’m just glad I spend my nights editing a book rather than in despair over Instagram videos of teenagers snatching my back squat 1RM. As usual this project became a little more comprehensive than originally planned and I hope that our readers will find some joy scanning through the knowledge in here.

Thank you, Agata Mossakowski, MD, for using your brilliant mind to help make this piece more readable and scavenge every little grammar mistake (because we all know, no grammar mistake is really "small"). Also a particularly big thank you for your help with the cover - mad illustrator skills!

To Ralph from nosh-pots.ch. Thanks for providing us with some cool pictures from one of your complete meals in a pot that we could use for our cover.

Thank you, Karl Larson, PhD, for sharing your expertise on protein metabolism and helpful advice with the manuscript.

References

Chapter 1.2

Nicholas A. Burd, Henrike M. Hamer, Bart Pennings, Wilbert F. Pellikaan, Joan M. G. Senden, Annemie P. Gijsen and Luc J. C. van Loon. Substantial Differences between Organ and Muscle Specific Tracer Incorporation Rates in a Lactating Dairy Cow. PLoS One. 2013; 8(6): e68109.

Jorn Trommelen. The Ultimate Guide to Muscle Protein Synthesis. https://www.nutritiontactics.com/measure-muscle-protein-synthesis/

Chapter 1.3

Figure 5 reprinted in modified version from Philip J. Atherton, Bethan E. Phillips, Daniel J. Wilkinson. Exercise and Regulation of Protein Metabolism. Prog Mol Biol Transl Sci. 2015;135:75-98, with permission by the lead or senior author.

Figure 6 reprinted in modified version from Cameron J. Mitchell, Tyler A. Churchward-Venne, Gianni Parise, Leeann Bellamy, Steven K. Baker, Kenneth Smith, Philip J. Atherton and Stuart M. Phillips. Acute Post-Exercise Myofibrillar Protein Synthesis Is Not Correlated with Resistance Training-Induced Muscle Hypertrophy in Young Men. PLoS One. 2014; 9(2): e89431, with permission by the lead or senior author.

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Figure 7 reprinted in modified version from Felipe Damas, Stuart M Phillips, Cleiton A Libardi, Felipe C Vechin, Manoel E Lixandrão, Paulo R Jannig, Luiz A R Costa, Aline V Bacurau, Tim Snijders, Gianni Parise, Valmor Tricoli, Hamilton Roschel, Carlos Ugrinowitsch. Resistance training-induced changes in integrated myofibrillar protein synthesis are related to hypertrophy only after attenuation of muscle damage.  J Physiol. 2016 Sep 15;594(18):5209-22. with permission by the lead or senior author.

Chapter 1.4

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Figure 10 reprinted in modified version from Kevin D. Tipton , Arny A. Ferrando , Stuart M. Phillips , David Doyle Jr. , and Robert R. Wolfe. Postexercise net protein synthesis in human muscle from orally administered amino acids. Am J Physiol. Endocrinol Metab. 1999, 276: E628-E634, with permission by the lead or senior author.

P. L. Greenhaff, L. G. Karagounis, N. Peirce, E. J. Simpson, M. Hazell, R. Layfield, H. Wackerhage, K. Smith, P. Atherton, A. Selby, and M. J. Rennie. Disassociation between the effects of amino acids and insulin on signaling, ubiquitin ligases, and protein turnover in human muscle. Am J Physiol Endocrinol Metab. 2008 Sep; 295(3): E595–E604.

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Figure 11 reprinted in modified version from Sophie Joanisse, Changhyun Lim, James McKendry, Jonathan C. Mcleod, Tanner Stokes and Stuart M. Phillips. Recent advances in understanding resistance exercise training-induced skeletal muscle hypertrophy in humans. Version 1. F1000Res. 2020; 9: F1000 Faculty Rev-141, with permission by the lead or senior author.

Chapter 1.5

Figure 12 reprinted in modified version from Daniel R Moore, Meghann J Robinson, Jessica L Fry, Jason E Tang, Elisa I Glover, Sarah B Wilkinson, Todd Prior, Mark A Tarnopolsky, Stuart M Phillips. Ingested protein dose response of muscle and albumin protein synthesis after resistance exercise in young men. Am J Clin Nutr. 2009 Jan;89(1):161-8, with permission by the lead or senior author.

Naomi M Cermak, Peter T Res, Lisette C P G M de Groot, Wim H M Saris, Luc J C van Loon. Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis.  Am J Clin Nutr. 2012 Dec;96(6):1454-64.

Figure 13 reprinted in modified version from Naomi M Cermak, Peter T Res, Lisette C P G M de Groot, Wim H M Saris, Luc J C van Loon. Protein supplementation augments the adaptive response of skeletal muscle to resistance-type exercise training: a meta-analysis.  Am J Clin Nutr. 2012 Dec;96(6):1454-64, with permission by the lead or senior author.

Chapter 2.1

Figure 14 reprinted in modified version from Daniel R Moore. Maximizing Post-exercise Anabolism: The Case for Relative Protein Intakes.  Front Nutr. 2019 Sep 10;6:147, with permission by the lead or senior author.

Chapter 2.2

Figure 15 reprinted in modified version from Daniel R Moore. Maximizing Post-exercise Anabolism: The Case for Relative Protein Intakes.  Front Nutr. 2019 Sep 10;6:147, with permission by the lead or senior author.

Chapter 2.3

Figure 16 reprinted in modified version from Daniel R Moore. Maximizing Post-exercise Anabolism: The Case for Relative Protein Intakes.  Front Nutr. 2019 Sep 10;6:147, with permission by the lead or senior author.

Chapter 2.4

Robert W Morton, Kevin T Murphy, Sean R McKellar, Brad J Schoenfeld, Menno Henselmans, Eric Helms, Alan A Aragon, Michaela C Devries, Laura Banfield, James W Krieger, and Stuart M Phillips. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018 Mar; 52(6): 376–384.

Figure 17 reprinted in modified version from Robert W Morton, Kevin T Murphy, Sean R McKellar, Brad J Schoenfeld, Menno Henselmans, Eric Helms, Alan A Aragon, Michaela C Devries, Laura Banfield, James W Krieger, and Stuart M Phillips. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018 Mar; 52(6): 376–384, with permission by the lead or senior author.

Chapter 3.1

Lindsey Ormond, Determining Protein Quality: The Current State Of Play. https://www.arlafoodsingredients.com/the-whey-and-protein-blog/research/determining-protein-quality-the-current-state-of-play/

Chapter 3.2

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Keith Baar, Karyn Esser. Phosphorylation of p70(S6k) correlates with increased skeletal muscle mass following resistance exercise Am J Physiol. 1999 Jan;276(1):C120-7.

Figure 20 reprinted in modified version from Keith Baar, Karyn Esser. Phosphorylation of p70(S6k) correlates with increased skeletal muscle mass following resistance exercise Am J Physiol. 1999 Jan;276(1):C120-7, with permission by the lead or senior author.

Daniel W. D. West, Stuart M. Phillips. 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.

Brad J. Schoenfeld. The mechanisms of muscle hypertrophy and their application to resistance training. J Strength Cond Res. 2010 Oct;24(10):2857-72.

Marcas M. Bamman, Brandon M. Roberts, Gregory R. Adams. Molecular Regulation of Exercise-Induced Muscle Fiber Hypertrophy.  Cold Spring Harb Perspect Med. 2018 Jun 1;8(6):a029751.

Matthew S. Brook, Daniel J. Wilkinson, William K Mitchell, Jonathan N. Lund, Nathaniel J. Szewczyk, Paul L. Greenhaff, Ken Smith, Philip J. Atherton.  Skeletal muscle hypertrophy adaptations predominate in the early stages of resistance exercise training, matching deuterium oxide-derived measures of muscle protein synthesis and mechanistic target of rapamycin complex 1 signaling.  FASEB J. 2015 Nov;29(11):4485-96.

Figure 22 reprinted in modified version from Matthew S. Brook, Daniel J. Wilkinson, William K Mitchell, Jonathan N. Lund, Nathaniel J. Szewczyk, Paul L. Greenhaff, Ken Smith, Philip J. Atherton.  Skeletal muscle hypertrophy adaptations predominate in the early stages of resistance exercise training, matching deuterium oxide-derived measures of muscle protein synthesis and mechanistic target of rapamycin complex 1 signaling.  FASEB J. 2015 Nov;29(11):4485-96, with permission by the lead or senior author.

C. Florian Bentzinger, Klaas Romanino, Dimitri Cloëtta, Shuo Lin, Joseph B. Mascarenhas, Filippo Oliveri, Jinyu Xia, Emilio Casanova, Céline F. Costa, Marijke Brink, Francesco Zorzato, Michael N. Hall, Markus A Rüegg. Skeletal muscle-specific ablation of raptor, but not of rictor, causes metabolic changes and results in muscle dystrophy. Cell Metab. 2008 Nov;8(5):411-24.

Perrine Castets, Shuo Lin, Nathalie Rion, Sabrina Di Fulvio, Klaas Romanino, Maitea Guridi, Stephan Frank, Lionel A. Tintignac, Michael Sinnreich, Markus A. Rüegg. Sustained activation of mTORC1 in skeletal muscle inhibits constitutive and starvation-induced autophagy and causes a severe, late-onset myopathy.  Cell Metab. 2013 May 7;17(5):731-44.

Louise Deldicque, C Sanchez Canedo, S Horman, I De Potter, L Bertrand, L Hue, M Francaux. Antagonistic effects of leucine and glutamine on the mTOR pathway in myogenic C2C12 cells. Amino Acids. 2008 Jun;35(1):147-55.

Figure 24 reprinted in modified version from Louis Deldicque, C Sanchez Canedo, S Horman, I De Potter, L Bertrand, L Hue, M Francaux. Antagonistic effects of leucine and glutamine on the mTOR pathway in myogenic C2C12 cells. Amino Acids. 2008 Jun;35(1):147-55, with permission by the lead or senior author.

Rachel L. Wolfson and David M. Sabatini. The dawn of the age of amino acid sensors for the mTORC1 pathway. Cell Metab. 2017 Aug 1; 26(2): 301–309.

Chapter 3.3

Tyler A. Churchward-Venne, Nicholas A. Burd, Cameron J. Mitchell, Daniel W. D. West, Andrew Philp, George R. Marcotte, Steven K. Baker, Keith Baar and Stuart M. Phillips. Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. J Physiol. 2012 Jun 1; 590(Pt 11): 2751–2765.

Figure 26 reprinted in modified version from Tyler A. Churchward-Venne, Nicholas A. Burd, Cameron J. Mitchell, Daniel W. D. West, Andrew Philp, George R. Marcotte, Steven K. Baker, Keith Baar and Stuart M. Phillips. Supplementation of a suboptimal protein dose with leucine or essential amino acids: effects on myofibrillar protein synthesis at rest and following resistance exercise in men. J Physiol. 2012 Jun 1; 590(Pt 11): 2751–2765, with permission by the lead or senior author.

David Sabatini. Introduction to mTOR and the Regulation of Growth. https://www.youtube.com/watch?v=EnIerDljc7g

Chapter 3.4

Stefan H.M. Gorissen, Astrid M.H. Horstman, Rinske Franssen, Julie J.R. Crombag, Henning T. Langer, Jörgen Bierau, Frederique Respondek, Luc J.C. van Loon. Ingestion of Wheat Protein Increases In Vivo Muscle Protein Synthesis Rates in Healthy Older Men in a Randomized Trial. J Nutr. 2016 Sep;146(9):1651-9.

Figure 28 reprinted in modified version from Stefan H.M. Gorissen, Astrid M.H. Horstman, Rinske Franssen, Julie J.R. Crombag, Henning T. Langer, Jörgen Bierau, Frederique Respondek, Luc J.C. van Loon. Ingestion of Wheat Protein Increases In Vivo Muscle Protein Synthesis Rates in Healthy Older Men in a Randomized Trial. J Nutr. 2016 Sep;146(9):1651-9, with permission by the lead or senior author.

Stephan van Vliet, Nicholas A. Burd, Luc J.C. van Loon. The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption.  J Nutr. 2015 Sep;145(9):1981-91.

Figure 29 reprinted in modified version from Stephan van Vliet, Nicholas A. Burd, Luc J.C. van Loon. The Skeletal Muscle Anabolic Response to Plant- versus Animal-Based Protein Consumption.  J Nutr. 2015 Sep;145(9):1981-91, with permission by the lead or senior author.

Amy Banaszek, Jeremy R. Townsend, David Bender, William C. Vantrease, Autumn C. Marshall, Kent D. Johnson. The Effects of Whey vs. Pea Protein on Physical Adaptations Following 8-Weeks of High-Intensity Functional Training (HIFT): A Pilot Study.  Sports (Basel). 2019 Jan 4;7(1):12.

Jordan M. Joy, Ryan P. Lowery, Jacob M. Wilson, Martin Purpura, Eduardo O. De Souza, Stephanie Mc Wilson, Douglas S Kalman, Joshua E Dudeck, Ralf Jäger. The effects of 8 weeks of whey or rice protein supplementation on body composition and exercise performance.  Nutr J. 2013 Jun 20;12:86.

Chapter 3.5

Mee-Sup Yoon. The Role of Mammalian Target of Rapamycin (mTOR) in Insulin Signaling. Nutrients. 2017 Nov; 9(11): 1176.

Gommaar D'Hulst, Inés Soro-Arnaiz, Evi Masschelein, Koen Veys, Gillian Fitzgerald, Benoit Smeuninx, Sunghoon Kim, Louise Deldicque, Bert Blaauw, Peter Carmeliet, Leigh Breen, Peppi Koivunen, Shi-Min Zhao, Katrien De Bock. PHD1 controls muscle mTORC1 in a hydroxylation-independent manner by stabilizing leucyl tRNA synthetase. Nat Commun. 2020 Jan 10;11(1):174.

Jorn Trommelen, Bart B.L. Groen, Henrike M. Hamer, Lisette C.P.G.M. de Groot, Luc J C van Loon. Exogenous insulin does not increase muscle protein synthesis rate when administered systemically: a systematic review.  Eur J Endocrinol. 2015 Jul;173(1):R25-34.

Figure 31 reprinted in modified version from Sarah Everman, Christian Meyer1 Lee Tran, Nyssa Hoffman, Chad C. Carroll, William L. Dedmon, and Christos S. Katsanos. Insulin does not stimulate muscle protein synthesis during increased plasma branched-chain amino acids alone but still decreases whole body proteolysis in humans. Am J Physiol Endocrinol Metab. 2016 Oct 1; 311(4): E671–E677, with permission by the lead or senior author.

Stefan H.M. Gorissen, Nicholas A. Burd, Henrike M. Hamer, Annemie P. Gijsen, Bart B. Groen, Luc J.C. van Loon. Carbohydrate coingestion delays dietary protein digestion and absorption but does not modulate postprandial muscle protein accretion.  J Clin Endocrinol Metab. 2014 Jun;99(6):2250-8.

Mee-Sup Yoon. The Role of Mammalian Target of Rapamycin (mTOR) in Insulin Signaling. Nutrients. 2017 Nov; 9(11): 1176.

Megan N. Roberts, Marita A. Wallace, Alexey A. Tomilov, Zeyu Zhou, George R. Marcotte, Dianna Tran, Gabriella Perez, Elena Gutierrez-Casado, Shinichiro Koike, Trina A. Knotts, Denise M. Imai, Stephen M. Griffey, Kyoungmi Kim, Kevork Hagopian, Marissa Z. McMackin, Fawaz G. Haj, Keith Baar, Gino A. Cortopassi, Jon J. Ramsey, Jose Alberto Lopez-Dominguez. A Ketogenic Diet Extends Longevity and Healthspan in Adult Mice. Cell Metab. 2017 Sep 5;26(3):539-546.e5.

Figure 32 reprinted in modified version from Megan N. Roberts, Marita A. Wallace, Alexey A. Tomilov, Zeyu Zhou, George R. Marcotte, Dianna Tran, Gabriella Perez, Elena Gutierrez-Casado, Shinichiro Koike, Trina A. Knotts, Denise M. Imai, Stephen M. Griffey, Kyoungmi Kim, Kevork Hagopian, Marissa Z. McMackin, Fawaz G. Haj, Keith Baar, Gino A. Cortopassi, Jon J. Ramsey, Jose Alberto Lopez-Dominguez. A Ketogenic Diet Extends Longevity and Healthspan in Adult Mice. Cell Metab. 2017 Sep 5;26(3):539-546.e5, with permission by the lead or senior author.

Stefan H.M. Gorissen, Nicholas A. Burd, Irene Fleur Kramer, Janneau van Kranenburg, Annemie P. Gijsen, Olav Rooyackers, Luc J.C. van Loon. Co-ingesting milk fat with micellar casein does not affect postprandial protein handling in healthy older men.  Clin Nutr. 2017 Apr;36(2):429-437.

Figure 33 reprinted in modified version from Stefan H.M. Gorissen, Nicholas A. Burd, Irene Fleur Kramer, Janneau van Kranenburg, Annemie P. Gijsen, Olav Rooyackers, Luc J.C. van Loon. Co-ingesting milk fat with micellar casein does not affect postprandial protein handling in healthy older men.  Clin Nutr. 2017 Apr;36(2):429-437, with permission by the lead or senior author.

Kostas Tsintzas, Robert Jones, Pardeep Pabla, Joanne Mallinson, David A Barrett, Dong-Hyun Kim, Scott Cooper, Amanda Davies, Tariq Taylor, Carolyn Chee, Christopher Gaffney, Luc J C van Loon, Francis B Stephens. Effect of acute and short-term dietary fat ingestion on postprandial skeletal muscle protein synthesis rates in middle-aged, overweight, and obese men. Am J Physiol Endocrinol Metab. 2020 Mar 1;318(3):E417-E429.

Chapter 4.1

D.K. Levenhagen, J.D. Gresham, M.G. Carlson, D.J. Maron, M.J. Borel, P.J. Flakoll. Postexercise nutrient intake timing in humans is critical to recovery of leg glucose and protein homeostasis. Am J Physiol Endocrinol Metab. 2001 Jun;280(6):E982-93.

B. Esmarck, J.L. Andersen, S. Olsen, E.A. Richter, M Mizuno and M. Kjær. Timing of postexercise protein intake is important for muscle hypertrophy with resistance training in elderly humans. J Physiol. 2001 Aug 15; 535(Pt 1): 301–311.

Lex B. Verdijk, Richard A.M. Jonkers, Benjamin G. Gleeson, Milou Beelen, Kenneth Meijer, Hans H.C.M. Savelberg, Will K.W.H. Wodzig, Paul Dendale, Luc J.C. van Loon. Protein supplementation before and after exercise does not further augment skeletal muscle hypertrophy after resistance training in elderly men. Am J Clin Nutr. 2009 Feb;89(2):608-16.

Benjamin T. Wall, Nicholas A. Burd, Rinske Franssen, Stefan H.M. Gorissen, Tim Snijders, Joan M. Senden, Annemie P. Gijsen, Luc J.C. van Loon. Presleep protein ingestion does not compromise the muscle protein synthetic response to protein ingested the following morning.  Am J Physiol Endocrinol Metab. 2016 Dec 1;311(6):E964-E973.

Figure 35 reprinted in modified version from Benjamin T. Wall, Nicholas A. Burd, Rinske Franssen, Stefan H.M. Gorissen, Tim Snijders, Joan M. Senden, Annemie P. Gijsen, Luc J.C. van Loon. Presleep protein ingestion does not compromise the muscle protein synthetic response to protein ingested the following morning.  Am J Physiol Endocrinol Metab. 2016 Dec 1;311(6):E964-E973, with permission by the lead or senior author.

Chapter 5

José L. Areta, Louise M. Burke, Megan L. Ross, Donny M. Camera, Daniel W.D. West, Elizabeth M. Broad, Nikki A. Jeacocke, Daniel R. Moore, Trent Stellingwerff, Stuart M. Phillips, John A. Hawley, Vernon G. Coffey. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis.  J Physiol. 2013 May 1;591(9):2319-31.

Figure 36 reprinted in modified version from José L. Areta, Louise M. Burke, Megan L. Ross, Donny M. Camera, Daniel W.D. West, Elizabeth M. Broad, Nikki A. Jeacocke, Daniel R. Moore, Trent Stellingwerff, Stuart M. Phillips, John A. Hawley, Vernon G. Coffey. Timing and distribution of protein ingestion during prolonged recovery from resistance exercise alters myofibrillar protein synthesis.  J Physiol. 2013 May 1;591(9):2319-31, with permission by the lead or senior author.

Chapter 6

Peter T. Res, Bart Groen, Bart Pennings, Milou Beelen, Gareth A. Wallis, Annemie P. Gijsen, Joan M.G. Senden, Luc J.C. van Loon. Protein ingestion before sleep improves postexercise overnight recovery.  Med Sci Sports Exerc. 2012 Aug;44(8):1560-9.

Figure 37 reprinted in modified version from Peter T. Res, Bart Groen, Bart Pennings, Milou Beelen, Gareth A. Wallis, Annemie P. Gijsen, Joan M.G. Senden, Luc J.C. van Loon. Protein ingestion before sleep improves postexercise overnight recovery.  Med Sci Sports Exerc. 2012 Aug;44(8):1560-9, with permission by the lead or senior author.

Tim Snijders, Peter T. Res, Joey S.J. Smeets, Stephan van Vliet, Janneau van Kranenburg, Kamiel Maase, Arie K. Kies, Lex B. Verdijk, Luc J.C. van Loon. Protein Ingestion before Sleep Increases Muscle Mass and Strength Gains during Prolonged Resistance-Type Exercise Training in Healthy Young Men.  J Nutr. 2015 Jun;145(6):1178-84.

Figure 38 reprinted in modified version from Tim Snijders, Peter T. Res, Joey S.J. Smeets, Stephan van Vliet, Janneau van Kranenburg, Kamiel Maase, Arie K. Kies, Lex B. Verdijk, Luc J.C. van Loon. Protein Ingestion before Sleep Increases Muscle Mass and Strength Gains during Prolonged Resistance-Type Exercise Training in Healthy Young Men.  J Nutr. 2015 Jun;145(6):1178-84, with permission by the lead or senior author.

Jorn Trommelen, Imre W.K. Kouw, Andrew M. Holwerda, Tim Snijders, Shona L. Halson, Ian Rollo, Lex B. Verdijk, Luc J.C. van Loon. Presleep dietary protein-derived amino acids are incorporated in myofibrillar protein during postexercise overnight recovery.  Am J Physiol Endocrinol Metab. 2018 May 1;314(5):E457-E467.

Andrew M. Holwerda, Maarten Overkamp, Kevin J.M. Paulussen, Joey S.J. Smeets, Janneau van Kranenburg, Evelien M.P. Backx, Annemie P. Gijsen, Joy P.B. Goessens, Lex B. Verdijk, Luc J.C. van Loon. Protein Supplementation after Exercise and before Sleep Does Not Further Augment Muscle Mass and Strength Gains during Resistance Exercise Training in Active Older Men. J Nutr. 2018 Nov 1;148(11):1723-1732.

Tim Snijders, Jorn Trommelen, Imre W.K. Kouw, Andrew M. Holwerda, Lex B. Verdijk, and Luc J.C. van Loon. The Impact of Pre-sleep Protein Ingestion on the Skeletal Muscle Adaptive Response to Exercise in Humans: An Update. Front Nutr. 2019; 6: 17.

Chapter 7

T. Brock Symons, Scott E. Schutzler, Tara L. Cocke, David L. Chinkes, Robert R. Wolfe, Douglas Paddon-Jones. Aging does not impair the anabolic response to a protein-rich meal.  Am J Clin Nutr. 2007 Aug;86(2):451-6.

Figure 39 reprinted in modified version from T. Brock Symons, Scott E. Schutzler, Tara L. Cocke, David L. Chinkes, Robert R. Wolfe, Douglas Paddon-Jones. Aging does not impair the anabolic response to a protein-rich meal.  Am J Clin Nutr. 2007 Aug;86(2):451-6, with permission by the lead or senior author.

Benjamin Toby Wall, Stefan H. Gorissen, Bart Pennings, René Koopman, Bart B.L. Groen, Lex B. Verdijk, and Luc J.C. van Loon. Aging Is Accompanied by a Blunted Muscle Protein Synthetic Response to Protein Ingestion. PLoS One. 2015; 10(11): e0140903.

Figure 40 reprinted in modified version from Benjamin Toby Wall, Stefan H. Gorissen, Bart Pennings, René Koopman, Bart B.L. Groen, Lex B. Verdijk, and Luc J.C. van Loon. Aging Is Accompanied by a Blunted Muscle Protein Synthetic Response to Protein Ingestion. PLoS One. 2015; 10(11): e0140903, with permission by the lead or senior author.

Daniel R. Moore, Tyler A. Churchward-Venne, Oliver Witard, Leigh Breen, Nicholas A. Burd, Kevin D. Tipton, Stuart M. Phillips. Protein Ingestion to Stimulate Myofibrillar Protein Synthesis Requires Greater Relative Protein Intakes in Healthy Older Versus Younger Men. Journals of Gerontology Series A: Biomedical Sciences and Medical Sciences, 70(1), 57-62.

Figure 41 reprinted in modified version from Daniel R. Moore, Tyler A. Churchward-Venne, Oliver Witard, Leigh Breen, Nicholas A. Burd, Kevin D. Tipton, Stuart M. Phillips. Protein Ingestion to Stimulate Myofibrillar Protein Synthesis Requires Greater Relative Protein Intakes in Healthy Older Versus Younger Men. J Gerontol A Biol Sci Med Sci, 70(1), 57-62, with permission by the lead or senior author.

Chapter 8

Thomas P. Wycherley Lisa J Moran, Peter M. Clifton, Manny Noakes, Grant D. Brinkworth. Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012 Dec;96(6):1281-98.

Figure 42 & 43 reprinted in modified version from Thomas P. Wycherley Lisa J Moran, Peter M. Clifton, Manny Noakes, Grant D. Brinkworth. Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomized controlled trials. Am J Clin Nutr. 2012 Dec;96(6):1281-98, with permission by the lead or senior author.

Amy J. Hector, Stuart M. Phillips. Protein Recommendations for Weight Loss in Elite Athletes: A Focus on Body Composition and Performance. Int J Sport Nutr Exerc Metab. 2018 Mar 1;28(2):170-177.

Figure 44 reprinted in modified version from Amy J. Hector, Stuart M. Phillips. Protein Recommendations for Weight Loss in Elite Athletes: A Focus on Body Composition and Performance. Int J Sport Nutr Exerc Metab. 2018 Mar 1;28(2):170-177, with permission by the lead or senior author.

Thomas M. Longland, Sara Y. Oikawa, Cameron J. Mitchell, Michaela C. Devries, Stuart M. Phillips. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr. 2016 Mar;103(3):738-46.

Figure 45 reprinted in modified version from Thomas M. Longland, Sara Y. Oikawa, Cameron J. Mitchell, Michaela C. Devries, Stuart M. Phillips. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr. 2016 Mar;103(3):738-46, with permission by the lead or senior author.

Chapter 9

Tyler A. Churchward-Venne, Philippe J.M. Pinckaers, Joey S.J. Smeets, Milan W. Betz, Joan M. Senden, Joy P.B. Goessens, Annemie P. Gijsen, Ian Rollo, Lex B. Verdijk, Luc J.C. van Loon. Dose-response effects of dietary protein on muscle protein synthesis during recovery from endurance exercise in young men: a double-blind randomized trial. Am J Clin Nutr. 2020 Aug 1;112(2):303-317.

Figure 46 & 47 & 48 reprinted in modified version from Tyler A. Churchward-Venne, Philippe J.M. Pinckaers, Joey S.J. Smeets, Milan W. Betz, Joan M. Senden, Joy P.B. Goessens, Annemie P. Gijsen, Ian Rollo, Lex B. Verdijk, Luc J.C. van Loon. Dose-response effects of dietary protein on muscle protein synthesis during recovery from endurance exercise in young men: a double-blind randomized trial. Am J Clin Nutr. 2020 Aug 1;112(2):303-317, with permission by the lead or senior author.

Daniel R Moore. Maximizing Post-exercise Anabolism: The Case for Relative Protein Intakes.  Front Nutr. 2019 Sep 10;6:147.

D. Travis Thomas, Kelly Anne Erdman, Louise M. Burke. Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance. J Acad Nutr Diet. 2016 Mar;116(3):501-528.

Chapter 11

Nisha Gaind. Huge US university cancels subscription with Elsevier. https://www.nature.com/articles/d41586-019-00758-x

Ian Graber-Stiehl. Science’s pirate queen. https://www.theverge.com/2018/2/8/16985666/alexandra-elbakyan-sci-hub-open-access-science-papers-lawsuit