14 12 2012
The sense and non-sense of pre- and post-workout nutrition
More than any other type of supplements, the entire industry has revolved around supplements that enhance or support the workout. To improve energy, performance, increases in muscle mass and recovery. If you believed the hype surrounding each type of ingredient, and had the money, you might well be taking as many as 30 different supplements prior to, during and after your workout, likely in nauseating quantities. But it can be quite difficult to make sense of not only what the body needs, but what will favorably affect your results in the short and long term. In this first installment we are going to be focusing largely on the most important part: the macronutrients. That means the food, as well as supplementary protein (amino acids), carbohydrates and fats you may or may not be using to replace or supplement that food, you need to take in around your workout. We will be discussing the best sources of macronutrients, timing and dosing in an in-depth fashion. A lot of the information here will likely seem logical if you have read the article “the basic biochemical principles of skeletal muscle hypertrophy” in the general section of this site, but I’m also aware that that article (even though it has short simple introductory passages at the start, and a cliff notes summary at the end of each section) can be a daunting read.
Defining the anabolic window
Although some old-school trainers and writers may still tell you the old fable that “exercise destroys muscle and nutrition and rest rebuild it”, it is a well understood scientific fact that resistance exercise is a direct anabolic signal. It increases the anabolic machinery directly through stimulation of the anabolic signal integrator mTORC1 and results in a drastic increase in various growth factors that sustain and prolong that anabolic effect, like IGF-1a, MGF and Wnt. Resistance exercise creates what is termed as an “anabolic window” of increased muscle protein synthesis (MPS) during which the increased effect of nutrients seems most effective. Although the anabolic window created by resistance exercise can last up to 48 hours (1), the effect seems to be most pronounced right around the time of exercise with increases in muscle protein synthesis of 100-150% above basal rates (2).
Protein ingested up to 24h after exercise still managed to increase MPS above that of unexercised individuals (3), but at this point the effect was unrelated to exercise load (and thus indicative of any type of exercise or an active lifestyle in general). These data do create interesting implications for “the bodybuilding lifestyle” because basically none of us go 48 hours without training, meaning literally every meal consumed every single day contributes to our muscle growth in some way, more than it would for a more sedentary individual and stresses the importance of the round-the-clock feeding we are all subject too, at least when the main goal is to increase muscle mass or strength. But the synergy is significantly greater in the window starting 45 mins prior to and up to 2h after a resistance training workout (13).
Leucine as the anabolic trigger
The importance of dietary protein, and its constituent amino acids, in skeletal muscle hypertrophy is well understood by all. After all large portions of the cell are made up of proteins, and especially in muscle, where the very contractile machinery we aim to increase in size to enhance muscle mass and strength is made up primarily of the contractile proteins actin and myosin. We distinguish 20 amino acids that are used in protein synthesis in the body, of which 10 are considered essential amino acids (and must always be ingested) or EAA, and 10 can be synthesized from the EAA under the right circumstances in the body, but are also quite abundant in the body. Aside from those there is a whole host of amino acid derivatives that have functional relevance to the cells optimal function. The EAA especially have been studied extensively in their ability to stimulate muscle protein synthesis and are considered absolutely necessary for health, well-being and in our case, muscle growth. Aside from the EAA glutamine is considered essential in this process as well, since a cell must be glutamine-loaded in order to be stimulated by EAA (reviewed here).
“When high doses of free form leucine are given by themselves or in addition to intact protein they seem to have no real effect on muscle protein synthesis.”
Among these amino acids there seems to be a more significant role for the branched chain amino acid (BCAA) leucine. When leucine is abundant in the area around the cell, it stimulates a transport protein on the cell’s surface that can permit the cell to absorb leucine by expelling glutamine. Leucine in the cell then initiates two distinct processes. The first is to localize the anabolic signaling complex mTORC1 to the lysosome, the area in the cell where it can be activated and assembled, and the second is directly stimulate the activation of mTORC1 by increasing production of its activating substrate phosphatidic acid (the entire process is reviewed in detail in this article). This sketches a good picture of the importance of leucine in skeletal muscle hypertrophy, and yet you’ll find that the supplement industry has often misinterpreted the importance of leucine, as you can tell by the wide variety of products containing free form L-leucine alone, or in combination with the other two BCAA’s, isoleucine and valine. When high doses of leucine are given by themselves (4) or in addition to intact protein (5,8) they seem to have no real effect on muscle protein synthesis. Magne et al. (5) concluded that the free form leucine would be rapidly digested and metabolized and therefor cause a lag between the availability of other essential amino acids and the transient anabolic response to the free form leucine. They therefor propose a model of leucine as an anabolic “trigger” (5,6). That works pretty much as it sounds. If you picture a gun, then pulling the trigger will fully and completely activate the gun’s machinery, however without bullets such an effort is not to much avail. Therefor the only time free form leucine should be given is in a complete mixture of free form essential amino acids in sufficient doses (~10g), which would be a fairly costly affair for most people to maintain. Perhaps also of note is that at least one study (7) actually saw more potent increases in some parts of the anabolic machinery using their control of non-essential amino acids than with their test products, free from leucine and citrulline (a derivative of the amino acid arginine). One possible explanation is that non-essential amino acid mixture supported the already present basal protein synthesis to a greater extent, while the perhaps greater stimulation with the test products was nullified by lack of other amino acids.
In short the research sketches a picture of leucine as an integral anabolic trigger for muscle protein synthesis, but only in the presence of other essential (and possibly non-essential) amino acids and in glutamine-loaded cells. So while we can conclude that free form leucine, whether given alone or in combination with intact proteins, is an absolute waste of time, the actual leucine content of intact proteins will go a long way in determining the quality of a protein.
Protein dosing and spacing
Another common misconception thrown around in regards to protein nutrition is that we can only use 20-30g of protein in a single sitting. This assumption is likely based on the research of Moore et al. (9) showing that ingestion of 40g of high quality protein only yielded the same effect on MPS as 20g of the same protein. The additional protein only lead to greater oxidation of the protein. Aside from a host of problems with this study such as the pre-infusion of labeled leucine as a tracer, we also need to consider the source (egg), form (liquid) and digestion rate of the protein. The current assumption in the literature is that ~25g of whey protein is the optimal dosing, but this is solely in regards to a fast-digested, liquid protein, ingested without anything else, in a fasted state, in young individuals. That dose will need to be seriously adjusted for protein source, bodyweight, gender and especially age (10,11). If we consider for example casein, which is slightly lower in leucine content, but takes upwards of 6 hours to digest, we could easily state that a dose of up to 3 times would still be effective for a single sitting, amounting to 75g. Of course digestion and absorption kinetics are not as linear as I would propose here, so that dose would still need to be adjusted downwards a bit, but this is merely an example to demonstrate that the amount of protein we can use in a single sitting is significantly higher than 25g and dependent on a great number of factors. Likewise increased oxidation of protein is also not necessarily a bad thing, it simply means a portion of your amino acids is being used as energy. Especially alanine and the extremely abundant glutamine are excellent substrates for gluconeogenesis, or the manufacture of glucose from amino acids. But because this process is less stimulating of insulin and the fact that this protein will likely be ingested instead of carbohydrates or fats, it’s basically a less fattening way of providing energy. We can probably state that for a simple whey protein shake 25-30g is probably an upper limit, keeping in mind that very few protein powders are actually 100% protein, and that this does not equate to 25-30g of powder, but likely 30-35g of powder.
The generally accepted daily dosing of protein for a performance and physique athlete is 2.2g per kg lean bodyweight (1g per pound). Research in this regard is still conflicting, but more recent research seems to at least validate the position that this number is near optimal, so barring newer conflicting data, we will maintain this figure. Because if you factor in that there is a limit to the amount of protein one can use at once (just not nearly as low as you may have been lead to believed) and that resistance exercise supports increased muscle protein synthesis for up to 48h, it should also become obvious now that we will be seeking to increase the frequency and spacing of protein intake across the day. In the interest of supporting maximal muscle growth it is therefore essential to eat multiple meals a day, spaced some 3 to maximally 4 hours apart. The use of slower digesting protein for any of these feedings that aren’t immediately prior or after your workout is also highly advised. Lean meats, eggs, cheese and milk in mixed macronutrient meals or protein shakes using casein instead of whey lend themselves to this purpose most of all. Their stimulation of MPS may actually exceed the time until your next feeding, but as alluded to previously, these kinetics are not linear, and the new intake will still cause a spike in blood amino acids and MPS above the current baseline.
Some people have pointed out to me that diet guru Lyle McDonald once suggested that feeding too frequently may adversely affect protein synthesis based on a study showing continuous infusion of amino acids lead to a tapering off of fractional synthetic rates in muscle. Aside from pointing out that even McDonald pointed out the possible errors in extrapolating this data, I want to state again, very clearly, that you cannot translate the results of an infusion to an ingestion. Ingestion is a large bolus dose of macronutrients that is digested, absorbed, processed and distributed gradually, leading to peaks and drops in blood levels. An infusion is a continuous maintenance of the same blood level which mimics an elevated BASAL level, and reduces the response to those nutrients. This is likely because the glutamine level in blood and cells level off, leading to a decreased expulsion of glutamine and a reduced uptake of leucine in the cell (read here for more information).
One needn’t exaggerate of course and sacrifice much needed sleep to get up and feed more frequently. It has been shown that protein ingestion before bed (12) is followed by normal protein digestion and absorption kinetics, meaning you can bridge a large part of this seeming gap by planning a meal rich in slow digesting proteins like casein, which can take up to 7-8 hours to fully digest, just prior to sleeping, thereby elevating plasma amino acid levels for much of the night and supporting protein synthesis.
Protein, exercise and muscle protein accretion
Before we delve into the intricacies of protein source and timing, it is perhaps important to understand the correlation between exercise and protein synthesis. Normally when we feed the result is an increase in muscle protein synthesis (MPS) via the mechanisms described in this review. In between meals, the fasted state, we tend to lose muscle protein. The protein synthesis caused by feeding replaces and replenishes the protein loss caused by fasting. This is why during periods of muscle accrual we tend to eat more frequent meals to minimize the time spent in a fasted state and spend more time during protein synthesis, but obviously the rate of manipulation in this regard is minimal if you know we can only use so much protein and boost MPS, with an excess being oxidized, at which point consuming more, more often will only lead to energy being stored as fat. That is why despite the highly anabolic effect of protein feeding you’ll never see anyone grow muscle just sitting around eating protein all day. The effect of resistance exercise also increases MPS, via many of the same mechanisms that protein feeding does, and probably a few others as well. The common observation in the literature however is that the effect of protein feeding and resistance exercise is synergistic, and while the effect of feeding is transient and limited to a few hours, the effect of exercise can last upwards of 48h. In the fasted state this elevation results in reduced amounts of protein lost, and during feeding the synergism leads to higher protein accrual, shifting the net protein balance in favor of muscle protein accumulation (13).
Protein source : Slow versus fast protein and everything in between
A major focal point of much of the research into supplementary protein adjacent to resistant exercise, especially of late, has focused excessively on the rate of digestion of the protein. Ever since the establishment of great variability of digestion rate we have coined the terms “fast and slow proteins”. The key protagonists in this discussion are whey and casein, the two fractions that make up milk protein. Whey is acid labile and an unusually fast digested protein , while casein is acid stable and curdles forming a slow digesting blob in the stomach. The result is that they have quite different patterns of amino acid appearance and different effects on protein synthesis and breakdown. An extremely fast appearance rate leads to a drastic increase in protein synthesis, but the resulting hyper-aminoacidemia also tapers off quickly, while a slowed rate of appearance leads to a sustained but more moderate elevation of amino acids in the blood. We will only be discussing whey and casein proteins from here on out. The supplement industry has since jumped the diversity bandwagon and produced a great many supplemental isolate proteins from various sources, but literally all of them have taken a backseat to milk proteins in practically every study. That is not to say they don’t help or increase MPS, they unequivocally do, but to a much lesser extent. There is definitely a place for rice, egg, meat, fish and soy protein in your diet, but then preferably in a mixed meal containing actual rice, eggs, meat, fish and soybeans, where they can provide more than their protein content. The aim of supplemental protein is to ensure adequate protein at the right time, and barring some form of allergy, there really is no excuse to settle for less than the best.
Whey protein has been the prodigy of the supplement industry, by far leading sales since bodybuilding supplements came in vogue up until now. Research also clearly demonstrates whey is by far the superior choice for pre and post-workout nutrition. That is the topic of this article, and we will be discussing it at length in a bit. Although I have been singing the praise of casein as an absolute must in the supplement arsenal for well over a decade, it wasn’t until the supplement industry realized they could make more money selling both as worthy supplements, instead of using casein as the cheap protein alternative to fool consumers, that magazines and trainers started suggesting some uses for casein, around 2004-2005, particularly as a protein source prior to bed. However still very few people seem to realize that micellar casein is probably by far the superior protein source for literally any other time of day other than around your workout. Previous research already demonstrated it, and new research continues to validate this (14). Not only is the area under the curve (an indication of absolute volume) for casein greater than for whey, the slower rate of appearance also leads to reduced oxidation and therefor greater peripheral uptake of amino acids. Phillips et al. (13) postulated that the higher quality of whey may have been related to a greater uptake by peripheral tissue rather than the splanchnic bed, but the Soop et al. study (14) clearly demonstrates an equal distribution of amino acids from both whey and casein across splanchnic and peripheral tissues, but that total uptake in both was greater for casein than for whey. Especially when you can’t eat frequently enough to stimulate protein synthesis around the clock, casein is a far better option to cover your basis as well. Using whey would almost necessitate feeding every 2.5h to reap the benefits it offers over casein. Of course adding a little whey to your casein to get a higher postprandial boost in MPS, and then have mostly casein to sustain it and prevent protein loss is an even better idea. Which is roughly the composition of milk protein, which is why I have been recommending milk as a staple in any diet for nearly 12 years now. Add to that that a liter of semi-skimmed milk is a complete meal at around 480 kcal with 48g of low glycemic sugar, 34g of protein and 15g of fat and sets you back less than half a buck. The fact that it is liquid and doesn’t need to be prepared makes it easy to use any time and be consumed on top of your normal meals to meet caloric and protein demands. During carb restriction (not something I practice outside of the last weeks of a diet) you can always switch to supplemental casein in water or extra casein in a bit of milk.
I also make a personal habit of supplementing my post-workout shake with cheap sources of protein on top of my 25-30g of whey as well, by mixing it in 500 ml of skim milk and adding 2 raw eggs. I don’t really understand why not more people make their shake with milk. It’s tastier, fuller, has additional proteins and you don’t need to add any carbs to it. I think there is some inane fear people have that mixing whey in anything, especially something containing slow digesting casein, will somehow affect the fast characteristics of whey, and that too is a good reason to include the Soop et al. (14) study here, because it was mostly designed to study the fate of the amino acids in whey and casein when they are co-ingested and it clearly shows that co-ingestion does not notably affect the fast nature of whey protein, with the mixed meal giving a distinct early and high peak in amino acid appearance, as well as a prolonged, moderate sustained effect as a result of the casein.
As we mentioned earlier though, whey remains the undisputed king of post-workout proteins as backed by the literature, and that is probably the result of its fast digestible nature, its high leucine content and complete amino acid profile. Central in this discussion were the studies by Tipton et al. (15,16). In the first study they examined the effect of a mix of 10g of free form essential amino acids + carbohydrate before and after the workout, and came to the surprising conclusion that when taken before the workout the effect on muscle protein synthesis was greater than when it was taken after the workout. This makes sense in a way since logically you would have an elevated amino acid level at the time the effect of your resistance exercise kicks in. Now before you go proclaiming that everyone should take their shake prior to their workout instead of after their workout, the second study was a copy of the first, but using intact whey protein instead of free form amino acids, and the results there were equal regardless of whether it was ingested before or immediately after the workout. But the effect was still slightly less pronounced than the results obtained with the free form amino acid mix. We typically define the optimal anabolic window as 45min prior and 2h after a workout, and for that reason, especially post-workout, whey is better suited. But that’s only post-workout, because as Burke et al. (19) recently demonstrated, when matched for leucine content, pre-workout, a slow digesting protein was able to match the results for a fast digesting one.
The two last mentioned studies by Tipton et al. already shed some light on the fact that there isn’t much difference in taking your whey protein shake just prior or just after your workout. Before seems slightly more favorable since you would have elevated blood amino acid levels as the effect of exercise kicks in, but in truth I’m not so sure this should be an either/or type of debate. There are a few things we know to be true. Exercise enhances the need for calories and consuming the bulk of calories around the time of the workout ensures they are maximally used in the anabolic window, with reduced chance of storing them as fat. The use of fast protein sources necessitates more frequent feeding. And lastly, we know that exercising in a fasted state leads to elevated AMPK (17), while training in a fed state does not (18). AMPK being one of the primary negative regulators of mTORC1, the key signal integrator in Muscle protein synthesis. Consider the time that elapses between a pre- and post-workout protein shake and you’ll soon begin to see the sense in using both. More than just protein it is important to make sure you are training in a fed state however, this can also be achieved by eating a full mixed nutrient meal 1 to 1.5h prior to your workout, then consuming your protein shake immediately after your workout and having another full meal 1.5 to 2h after that.
The role of carbohydrates
A great deal of attention in regards to pre-and post-workout nutrition is given to the carbohydrate content. This most likely stems from the fact that most of the older research focused heavily on typical endurance exercise and performance where glycogen replenishment is significantly more important. The importance of carbohydrates has oft been overstated by supplement manufacturers in an attempt to lace their product with cheap sugars, and claiming you will reap the benefits of the increased insulin boost. While we know insulin to have an anabolic function that is absolutely required for muscle protein synthesis, we also know that physiological insulin levels function much more like a permissive on/off switch(see the basic biochemical principles of skeletal muscle hypertrophy) where some insulin is required, but more has no effect (an amount estimated around 5mU/L (20)). Increases up to 30mU/L still managed to reduce Muscle protein breakdown by over 50% and therefor slightly enhance muscle protein synthesis, but higher levels had no further effect. What few people seem to realize however is that whey protein itself, and leucine especially, already increase insulin levels well above that level without further addition of carbohydrates. Carbohydrates alone (21,22) or in combination with protein (23) have no effect on muscle protein synthesis whatsoever.
As a conclusion there is no necessity to add carbohydrates to your pre-and post-workout shakes, and most certainly not to add extremely high glycemic fast sugars that will result in the faster deposition of fat with caloric spillover. Some healthier choices of carbs can be added however because any type of exercise depletes glycogen, and especially in a post-workout meal some carbohydrates are good to replenish glycogen stores while the muscle is still primed to absorb the majority of it due to the exercise induced upregulation of glycogen synthase. Training in a glycogen-deprived state also does not reduce the anabolic response to exercise (24) but keep in mind that such a state does increase glucagon release and stimulates gluconeogenesis to produce glucose from amino acids, and therefore less amino acids end up reaching the muscle. When consuming a diet that is overall low in carbohydrates, doses of protein should likely be adjusted upward to ensure maximal elevation of plasma amino acids. But in a carbohydrate sufficient diet there is really no need to add a lot of additional carbohydrates around the workout, a dose matching your amount of protein should probably be as high as you go.
The role of dietary fat
The importance of fat in this context isn’t very well researched. The general assumption is that a high fat content is to be avoided at all cost, because a bolus increase in fatty acids hinders insulin functioning and nutrient uptake, and leads to a high amount of ceramide production, which is a direct negative regulator of mTORC1. Although some research suggests a possible use for certain fats, no actual logic behind its possible benefits have been found to suggest one should purposely increase the fat content of workout nutrition. Omega-3 fatty acids (25) have been shown to lead to increased muscle protein synthesis, but this was demonstrated in an 8 week protocol where the omega-3 wasn’t actually taken inside the workout window, and the benefit is largely ascribed to a higher cumulative omega-3 content in muscle compared to other fatty acids after a period of taking them. More interestingly perhaps is the research (26) showing that full-fat milk yielded better results in this regard than energetically matched skim milk, even though fat itself has no effect on MPS (27). Phillips et al. (13) proposed that the fat somehow altered the kinetics of the protein and possibly the distribution, but to date there is no conclusive evidence to corroborate or elucidate this finding. As a result the prudent conclusion is that while one shouldn’t avoid fat in pre- and post-workout nutrition when it is already present (mixed meal or the use of milk or eggs in shakes), but that there is certainly no rationale for adding any particular fats or having a higher fat content in these meals. If anything, total fat content should be minimal.
After this lengthy review we can make a few firm conclusions in regard to pre- and postworkout nutrition. We have established there is an anabolic window that is created by exercise that lasts up to 48h during which a synergistic effect with high protein feeding, resulting in muscle accrual, is attained. The most optimal synergism between protein feeding and exercise is obtained during the smaller window of 1h prior to, and <2h after the workout. Because of the importance of training in a fed state to support muscle protein synthesis, and the increased requirement for nutrients during this tight window, it is strongly advised to feed both prior to and after a workout. The pre-workout meal can be either a full solid form mixed meal high in protein, or a high quality protein shake. In this particular case the rate of digestibility is less relevant. The post-workout meal is preferably a liquid meal containing a high content of whey protein (~30g) that is ingested immediately after or even near the end of the workout. Both meals can, but do not necessarily need to contain carbohydrates and it is wise not to exaggerate in the dose of carbohydrates, and select the source wisely, with a greater preference for more lower glycemic carbohydrates as the dose increases. Some fat can be included in the meal, but it is probably wise to steer clear of high fat meals during this window.
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