Chapters
00:00 Start
00:15 Our Study
00:42 Performance Impact
01:35 Fasted Performance
02:14 Psychological Effect
09:00 Carbohydrate Timing
13:27 Our Conclusion
Transcript
Do you need to consume carbs before a workout to maximize performance? And if so, how many grams of carbs do you need pre-workout to optimize your gains? To answer this question, I got a research team together and we looked at all the available studies comparing different carbohydrate intakes and measuring strength training performance.
This was actually the first systematic literature review on this topic. Up until this point, all reviews have been narrative reviews, which are essentially opinion pieces where the offers are free to include and not include studies as they choose. In our case, we literally included all the available studies. We found 22 relevant studies. Of those, 11 found no significant effects of pre-workout carbohydrate consumption or workout performance. 11 of those did over the 22 studies in total that we found. 14 of those found no significant differences in performance of the workout with higher versus lower carbohydrate intakes. So the majority of studies is a big picture. If you did not find effects of carbohydrate intake on how strong you are or how much volume you can do in a workout.
Of the eight studies that did find significant between group differences. Two of those interestingly favored lower carbs and six of those favored higher carbs. So overall, there was some trend for benefits of higher carbohydrate intakes. Now, if we zoom in on the context of the studies in which carbohydrate intake had a beneficial effect on performance, we find that in those studies, the higher carbohydrate intake group in all cases also had a higher energy intake. In fact, the placebo group or the lower carbohydrate intake group often received no energy intake at all. So they had to lower energy intake and they were actually training in an overnight fasted condition. In many cases.
So the condition was usually one group goes to the lab in the morning after an overnight fast, doesn’t consume anything, doesn’t work out. Therefore training completely fasted and the other group receives carbohydrate intake essentially a breakfast before they do the workout. And in that case, of course, we cannot say that it was the carbohydrate intake per se, or simply the energy intake in general that had a positive effect on performance. The lack of a proper placebo control is particularly confounding, because in some of the studies, we found that when the higher carbohydrate group receiving like a dextrose supplement or something was compared to nothing, so not even a placebo, there was a beneficial effect of higher carbs versus a lower carbs, meaning a beneficial effect of receiving the supplement versus not receiving the supplement. But this could have easily been a non metabolic effect or placebo effect or something else, because another group was compared in some of the studies where they received a placebo that was matched in texture and taste to the carbohydrate supplement. And then they found that there was no further benefit compared to the placebo.
There was also a study in which they had the placebo, either liquids or solids. So it didn’t actually have any energy. It was a placebo breakfast. And they found that the placebo breakfast. So it was like a modified to gel product, improved performance more than the liquid supplement. And they found that it correlated with hunger. Subsequent research has not clearly shown that hunger is really a mediating factor there. But clearly there are non physiological effects. There are psychological effects, mental effects that go on in these studies that can influence performance as well. So just the knowledge of having a breakfast, knowing that you’re not fasted or thinking at least that you’re not fasted and consuming something might also have an effect. We also have some studies in which carbohydrate a mouth, rinsing where you spit it out and you don’t actually swallow the carbs. I’m sure that will be clipped has a positive effect on performance. So just rinsing some Gatorade, for example, in your mouth and spitting it out can improve performance. And that seems to be mediated by dopaminergic receptors that are activated by carbs in the mouth or some other non metabolic effect. So clearly there are psychological effects going on here further support for the lack of a physiological effect of carbohydrate intake comes from dose response studies.
Studies in which they measured multiple carbohydrate intake such as low, medium and high, and they looked at the effect on performance. In those studies, we typically see that if there is any effect whatsoever, there is no effect of increasing the carbohydrate content. For example, one of the studies by cranks, it all looked at 15, 30 and 60g of carbohydrate per hour. And they found that all of those seem to be a little better for performance than not consuming anything. But 15g was already enough to maximize performance in that study. In fact, 15g had the absolute highest performance, not significantly different than the other groups. So not even a trend in favor of higher carbohydrate intakes having a more positive effect on how many reps you can do in a gym. So overall, we can say it’s likely suboptimal to train fasted. You might not have the same performance if you’re training fasted then otherwise.
However, it’s not actually that massive of a difference to begin with. If there is an effect, is that the effect is likely psychological, and if there is a non psychological effect, much of that is likely offset by even a very low carbohydrate intake. So think all message is essentially here that you want to consume something. You don’t want to try and fasted, but even 15g of carbohydrates is probably enough, especially if you also add some protein to that, which I also recommend to fuel embolism. So if you have something like 20g of protein minimum and 15g of carbohydrate minimum, you’re probably set in terms of workout performance. There is a caveat, which I’ll discuss in a moment, but first, why is it the case that we hear so many things about carbs being beneficial? You need carbs for energy, right? And we don’t see effects in most of the studies on performance. How can it be the reason you might have benefits from carbohydrates before a workout is because the body turns glucose into glycogen that stores in your muscles, and it burns up that glycogen via the glycolytic system to produce energy.
Now, the amount of glycogen that the body burns in a session simply isn’t that high. A good training session might burn some 300 to 500 calories and above basal. It might even be lower because much of the workout you’re not actually lifting. Right. So we do a set, maybe that’s 30s or something. And then most people rest much longer than that. So the rest to work ratio is really in favor of rest during most workouts. Moreover, eccentric muscle contractions are very energy efficient, so they don’t actually require that much energy compared to concentric only exercise. That’s why if you do something like bicycling, where you have nonstop concentrated muscle actions, you burn more energy per minute than if you do strength training and the requirements for glycogen can be much higher with something like repeated sprints on a bicycle, ergometer, or rowing.
Any type of high intensity interval training typically has a much higher requirement for glycogen than strength training. If we ran some exact numbers on those 300 to 500 calories, we see that the aerobic system still has a very large impact. It’s like 20 to 70% depending on which study you look at. So that’s mostly fueled by fat, because the rest periods allow the body to still produce most of its energy from fat. And if you subtract that, let’s go with the lowest part of 20%. Then we also have to subtract the creatine false fat part of the energy production. So that’s like the free main energy production systems that we have. You can essentially produce energy anaerobically. Or you can produce it from the creatine phosphate system, which relies on stored creatine phosphate bonds, which allow the body to rapidly produce some ATP. So this is kind of ATP. That is energy which is directly available. So if we subtract that which is 16 to 31% of the energy that during a typical set, then we are left with say 64% glycolytic component. So 64% of energy that the body would need actual carbohydrates for to burn glycogen. And we’re using that upper end of the 500 calorie energy expenditure from our workout. Then we are looking at 80g of carbohydrates to fuel a typical session. And if we assume about 500g of glycogen storage for a typical athlete, then we are looking at 16% glycogen depletion.
That’s obviously not nearly enough to disrupt neuromuscular functioning. You just don’t burn enough glycogen in a workout to empty the gas tank, basically. And indeed, if we look at the literature on glycogen depletion, many studies have looked at this. Then the largest depletion that we see from a given workout, even in bodybuilders doing many, many sets in a day, for example, we find that the highest level of depletion is 39% or 41% if you include eyes looking at exercise. So basically 40% max. Now it turns out that you need around 40% or higher glycogen depletion to significantly disrupt neuromuscular functioning. It takes glycogen levels of approximately 250 to 300 minimal per kilogram dry weight to start interfering with neuromuscular functioning and contractile functioning of the muscle. So even a very high volume workout generally does not induce enough glycogen depletion to empty the gas tank, and also that you don’t have enough energy to perform.
Moreover, many of the carbohydrates that you consume before a workout actually are essentially too late because those carbs are not in time to be digested, absorbed, and put into the muscle as glycogen, and therefore being available for energy production in that given workout. So the amount of carbohydrate intake that you consume before the workout actually doesn’t matter as much as how many carbs you ate in between the last two workouts. In general.
I think a very telling example study is the one by essence Gustafsson and. They found 28% depletion in the quads after five sets each of from squats, back squats, leg presses, and leg extensions to failure at 12 rep max. So it’s $0.20 to failure in bodybuilders. And then they found 28% depletion in the quads. However, there are some studies in which volumes of ten plus sets by the muscle group do actually cause enough glycogen disruption, possibly in some of the highest threshold motor units, especially specifically the type two muscle fibers, to potentially interfere with performance. And if we zoom in specifically on studies of 11 plus sets per muscle group per session, then we do see a trend that the majority of studies starts favoring higher carbohydrate intakes, or at least carbs versus no carbs. Because again, none of these studies or Isocal, they didn’t equate for total energy content. Still, the trend, even in those conditions, is more clearly in favor of higher carbs. Then, if you look at the studies. Why do you have seven or fewer sets for a muscle group per session? Now is a tangent.
In my view, you shouldn’t be doing ten plus sets per muscle group progression anyway. There are multiple lines of research showing that you get sharply diminishing returns and essentially no more benefits. Once you go past around six deaths per muscle group, a session that turns into junk volume and you mainly do more muscle damage, you stimulate more muscle protein breakdown. But there doesn’t seem to be a big additional increase in muscle protein synthesis. So in my view, you’re much better off splitting that volume up and doing five of those say, ten sets in a different workout rather than doing ten sets for a muscle group on that one day. So I’m definitely not a fan of typical lag days or just days where you do super high volume once per week for a certain muscle group. Anyway, that’s a topic for a different video if you’re interested in more details about that, both in the comments and I might do a full video on that.
Back to carbs. After our review, a meta analysis was published on the same topic, and it replicated our findings almost to the letter reading their conclusions. Carbohydrate ingestion has an organic effect, meaning performance enhancing effects on resistance training performance. Where session duration was longer than 45 minutes and the fast duration was at least eight hours. Conversely, carbohydrate ingestion did not significantly affect performance when session durations were shorter than 45 minutes or fast durations shorter than eight hours.
Those findings are almost exactly in line with our findings. Basically, there is no effect in settings where you are not training fasted and you’re not doing a super high volume per session. In their case, they looked at minutes per session, and I’m not a fan of that because glycogen storage is local. So if you do a full body workout and you are training a lot of muscle groups, you might have a very long session. But that does not actually increase your glycogen requirements, because only to sets per muscle group matter for the glycogen depletion for that muscle groups. That body also has some glycogen in the liver, but by and large a muscle relies on that glycogen stored in that specific muscle. So it’s a local reservoir of energy essentially that the muscle has. And it doesn’t matter if you also train another muscle group, it’s not going to take energy from the biceps. It’s not going to take glycogen from the biceps to fuel performance into quads. Actually, that’s not possible in the body. That’s reservoir of glycogen. That’s in the biceps can only be used by the biceps. So session duration doesn’t matter. It also doesn’t matter because if you take very long rest intervals that actually reduces given the same volume, the energy requirements of the session. Whereas if you use very short rest intervals, you can do even too much volume, potentially in 45 minutes if you do some crazy drops at protocol, for example. So I think it’s better to look at sets per muscle group for workouts. And there the threshold seems to be around ten sets that we start seeing. Okay, if you do that or if you do multiple workouts like on a given day, then there might be benefits of higher carbohydrate intakes pre-workout.
If you’re not doing that, and if you’re not training fasted, then there really isn’t any positive meaningful effect of carbs on your workouts. So our conclusion overall was based on the inconclusive evidence and potential for benefits. But don’t harm strength. Trainees are advised to consume at least 15g of carbohydrates and at least 0.3g/kg protein, but 20g for most individuals minimum within three hours of their training sessions. If the workout contains 11 or more shots per muscle group, or there is another high intensity workout plan that day for the same musculature, same allocators are important. Higher carbohydrate intakes up to 1.2g/kg per hour, so that’s a lot of carbohydrate may be warranted to maximize glycogen resurfaces in between workouts. So for most individuals, main take all message is within three hours of a workout. Consume a meal, which can be a shake or anything with at least 15g of carbohydrates. At least say 20g of protein, and then you’re probably covered. Unless you’re doing a super high volume session, which you probably shouldn’t be doing anyway. But if you are, then you might benefit from some extra workout carbs. Even then, though, it’s more important how many carbs you consumed in the whole previous day or the whole period in between your last workout and this workout, rather than how many carbs exactly are in your pre-workout meal?
So for most individuals that are not training fasted, not doing crazy high volumes, you really don’t have to worry much about pre-workout carbs. Just make sure you’re not training completely fasted and you are fine. If you like this type of evidence based content, I’d be honored if you like and subscribe. you might be interested in the online Arts certification course. You’ll learn absolutely everything you need to know to get results like these. The link is in the description. All right. Back to the video.
