I’ve been asked a few times lately about the current carbohydrate recommendations. The following guidelines are from Chapter 22: “Nutrition for Endurance Training and Competition” of “Endurance Training: Science and Practice, Second Edition,” edited by Iñigo Mujika. This chapter is written by Dr. Louise Burke, who is arguably the best high-performance nutrition researcher in the world right now.
I’ll give you some of my additional thoughts below.
All amounts are presented in grams (g) of carbohydrate. Sometimes this will be “g/kg” which is grams of carbohydrate per kg of bodyweight. Sometimes there will also be a time component, g/kg/hour, or g/kg/day.
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Day Before:
Training/racing <90 minutes: Day before is 7-12g/kg.
Training/racing >90 minutes: 36-48 hours of 7-12g/kg/day
Pre-workout:
1-4g/kg CHO consumed 1-4 hours before training/racing
During Workout:
Training/racing 45 minutes or less: no fueling needed
Training/racing 45-75 minutes: “small amounts including mouth rinse” (we’ll talk more about this later.
Training/racing 1-2.5 hours: 30-60g/hour.
Training/racing 2.5 hours plus: up to 90g/hour
Post workout:
“Speedy refueling:” <8 hours between efforts, 1-1.2g/kg/hour for four hours.
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Now, some thoughts of my own. “But coach Joe, those are the recommendations of science, why could you have any other thoughts other than those above?!?!” Well first, because they don’t cover every situation, and second because we know that some coaches and athletes do things slightly differently, so it’s worth chatting about. Also, there’s a little lost in translating the “how” of these recommendations.
First: Individual differences. In a perfect world, you’re able to go get a substrate utilization test which tells you exactly how many grams of carbs and fat you burn per hour at all intensities. Then you can know exactly how much you need to be replacing, and you then are able to just fuel for what you need! Unfortunately, this kind of thing isn’t available for everyone, nor does this kind of testing/system work anything like as well as you want unless you’re testing frequently, which is even more expensive and time consuming.
As a result, the recommendations above aren’t perfectly tailored to you, but are instead based off the results of that kind of testing for a bunch of fairly well-trained athletes.
If you aren’t a well-trained athlete this means you might not need to fuel this much. BUT, you probably don’t need to change it as much as you think. Most of the limitations of these recommendations are how much food your gut can process. It’s not a calorie-burning problem, it’s a calorie consumption problem. This means that for an elite athlete, they might be able to burn ~1500 calories/hour, but even if they take 120g/CHO/hour (a mind-blowing amount), they’re still only able to take in 480 calories, or LESS THAN A THIRD of what they’re burning. This means that even if you’re an athlete who can only burn 750 calories per hour, even still taking in 120g/hour (again, a HUGE amount) is barely covering 60% of your burn.
The real key is to practice! Try doing a long hard workout or race that you know the outcome, and try different amounts and see how your head and body react. If you’re fastest at 40g/hour, then by all means consume that little, but don’t just assume that because you aren’t riding the tour de France that you don’t need to fuel very much. TEST IT.
Second: Easy workouts. The above recommendations don’t really talk about intensity. And as we know, going balls-out for two hours is pretty different from a nice mellow two-hour noodle.
My thoughts:
-90m or less of low-intensity: No need to fuel (but it’s certainly not bad to have something!)
-90m or longer of low- intensity: 40-60g/hour
Third: “Small amount or mouth rinse.” This refers to some studies finding that in hard efforts shorter than 90 minutes that a mouth rinse of a zero-calorie artificial sweetener increased performance. This is interesting, because of the “zero calorie,” which means that you aren’t actually FUELING more. The proposed mechanism here is that your body is always holding a little in reserve. If you run the gas tank to literally zero, you die. So the body keeps a fairly large reserve. If you take in a small amount of carbs (or do the mouth rinse thing), you’re essentially telling the body that more gas is coming into the tank, so it can let some OUT of the tank. No, this doesn’t put you at risk of going to zero, but it WILL allow you to go a little faster. For me, I usually recommend a 20-30g gel taken right after the warmup and leading into the intervals, or in the middle of a 45-90 minute race.
Fourth: Break That Fast. These recommendations also don’t really talk about what happens if you have a late-morning or afternoon workout. For example, I usually train at 10AM. This means I should have 1-4g/kg 1-4 hours prior. BUT I WAKE UP AT 4:30AM. So should I wait to have breakfast until an hour before? No. I have a snack around 5:00AM so that I’m not empty from the night, and then I’ll have a 1-2g/kg breakfast at 8:00AM. My general recommendation for most athletes is to start with a 1g/kg meal two hours before a training session.
Fifth: Topping off. Especially if you’re doing a morning workout, it can be good to keep working on that over-night glycogen depletion by having another 20-30g/CHO 15-30 minutes before the workout.
Sixth: Old Carbs vs New Carbs:
Many of you reading this will have grown up with VERY different recommendations. Most of this is because we used to rely on single-sugar gels or drinks, like an original “Gu” brand gel. We learned the hard way pretty quickly that trying to go above 50-60g/hour would result in all sorts of shitty (see what I did there?) results. This is likely because individual sugars have their own transporter “tunnels” out of the gut. And if you try to take in, say, 80g of fructose/hour, you quickly back up the tunnel, resulting in a lot of extra fructose in the gut, which the body tries to dilute by bringing water back into the gut, resulting in both dehydration and stomach bloat. In the last few years, however, food nerds have figured out that if you combine two different sugars into a “soluble starch” it allows you to take in the equivalent of 60g/hour of one sugar, AND 60g/hour of another sugar. This then allows you to get up to the numbers seen in pro sports without the gut-bomb effect of the old gels.
NOW, an important factor to keep in mind is that mixing and matching can kinda fuck you up!
If you’re taking in one of the new soluble starches AND a sugary drink, or real food, you can all of a sudden have too much of a certain sugar, and get that same gut bomb result of the old gels. Thus I do not recommend mixing and matching carb sources during a high-intake effort!
As of April 2024 I’m a big fan of the Precision Hydration gels, Maurten’s are good but suuuper expensive, Never Second are good too, as well as SIS.
