Carbs At 90g Per Hour And Blood Sugar Crash

Thanks for posting this question! I have had similar issues recently so definitely will continue following this thread. I can say that last year I didn’t have any issues taking on as many carbs as I wanted. This year after a few months off (I know, too long) I jumped right into 90/hr and had similar issues to what you are talking about. I backed it down to about 60/hr and I haven’t had the issues since. Maybe try lowering the amount and see if that helps? I plan to start increasing slowly over the next few weeks/months and am hoping to get back to 90+.

Not to derail the thread, but side note - Have seen quite a few posters talk about sugar and the downsides on your dental health in this thread and others. To me it seems that as long as you don’t let it sit on your teeth afterwards it shouldn’t be a big deal. Its detrimental when it is allowed to hang around and aid in the growth of bacteria. I confirmed this with my dentist but would be interested to hear if anyone has better info than what my dentist has shared. Their only feedback was to rinse your mouth out with water after taking in carbs and also brush after workouts.

1 Like

Try switching to a 100% glucose mixture for training. Fructose has too many negative side-effects to be consumed in such quantities outside of racing. Especially in liquid form.

1 Like

Insulin response is regulated differently and slower (no crashing) under exercise than at rest. How do you know this is insulin related and not intensity or some other combination? The scientific method and real medical professionals is your best resource.

1 Like

Dont mix up hyper with hypo…

Hyper: too much sugar (rather thirsty)
Hypo: not enough sugar (ergo desire to eat desperately)


Yes, as I said earlier, the crash comes later.

I don’t, but the symptoms are very similar to the classic blood-sugar “crash”. It’s not a matter of losing steam during a workout, or low energy, but that panicked cold-sweat feeling that’s only alleviated by eating everything I can lay hands on.

Fair enough. I’ve already reached out to my PC, though in my experience a lot of this stuff is a bit off the map for general practitioners. This thread is just an attempt to see if others have experienced similar phenomena.

1 Like

I had the same thing. I stopped cramming my face with gels, blocks, and other simple sugars…problem solved.

It is heretical to suggest on TR, but maybe it isn’t the best idea for a person’s overall health to be taking large amounts of these “food” items? These are scientifically formulated sugars made as “simple” as possible. Nate talked on one of the recent podcasts about taking pure cake icing. As physically stressful as cycling is, I am wondering if anyone else is stopping, scratching their head, and asking if it is helping to overdo it on these “foods” that are terrible for your health. You don’t see TdF riders slamming 5 gels/hr for 5 hours a day.



1 Like


Swallowed in bars, gels and stirred into drinks, riders consume around 250 calories or 60g of carbohydrate per hour. “Riders take in energy little and often — 36g of carbohydrate from their drink every hour with a gel or bar every 30 minutes as well,” says Barraclough.

During the longest stages, carbohydrate intake can jump to 80 or 90g per hour — but the key is to start early. “If riders don’t fuel and drink properly, they will not be in contention when it comes to the critical part and finale of a stage,” says Pete Slater, co-founder of OTE Sports.

“Riders start taking drink, food and gels on board as soon as they get going.”

1 Like

(Disclaimer: Participating in a Grand Tour is about the least healthy activity a human can engage in.)


yeah, probably up there somewhere!!

I don’t think 5 gels ph is anything special for those guys - that’s only 435 calories (edit - that’s a lower rate than I’d burn doing taku!)

1 Like

Take a closer look at those links - tons of stuff there that is not isotonic gel. The point I am trying to make is that it is very important to differentiate between what kind of carbohydrate is ingested. There are bars, rice cakes, fats, proteins all thrown in there for nutrition. Not just isotonic gels and sugar bloks + drink mix. To say that all these carbohydrates are affecting your body in the same way is overly simplistic, and that a goal of just “get the sugar in” creates the problem described by the OP.

I’m speaking from personal experience. I spent 18 months focusing on on-the-bike fueling, using gels, drink mixes, and ClifBar Shot Bloks to get to 100g/hr for rides between 1800kJ and 3000kJ. I started having the same problems as the OP. I switched to include all different kinds of fuel - bagels, cereal, rice bars, Clif Bars, whole wheat breads, sandwiches, fruit juice, etc, in addition to gels and Shot Bloks. The difference was significant. I cut the total number of carbs ingested by 20 or so (so down to about 80g/hr), but I also eliminated the sugar crash that I had been experiencing.

If you look closely, that is exactly what these pro riders are doing - mixing and matching different combinations of foods and forms of carbohydrate to avoid crashing. Could they do 5 gels/hour for 3 weeks on end? Of course they could, they have sponsors who will give them whatever they want or need to perform. But they don’t.

1 Like

Is there any ballpark amount that estimates if you are well nourished the night prior (you eat a proper dinner), what your glycogen stores are first thing in the morning?
For those of us that train first thing right out of bed with no ability to eat prior, and can only retain carbs while on the bike, just wondering what the on-board stores could be to properly estimate what needs to be consumed to avoid “running out” and the fun that comes when that occurs - mental fog, hollow legs, increased RPE, etc.

I guess that depends on your FTP and how much glycogen you as an individual can store in the topped up state?

If I use myself as an example:
when I do long SS intervals @ 90% of FTP I consume just over 800kCal/hour

If I fuel with 90 grams of carbohydrate per hour i take in 360kCal/hour.

Which means I am turning a deficit of 440kCal/hour. So I am digging in to the stored glycogen fast! I don’t know how much I have in “storage”, but the difference of fueling and not fueling at those intensities are big. Also it makes me less hungry after the ride, not more hungty.

Screen Shot 2021-01-13 at 10.06.41 AM

1 Like

I’m in a similiar boat, I am outputting 960calories/hr @ 90%, and same math as you with the 360cal/hr input I am at a 600 deficit.
If I take what @ColoradoJames has pasted, while it talks that muscle glycogen is high, it doesn’t say what that means in terms of any sort of value. And appreciate that this will all be individual dependent.

I really notice I start to fade around the 45-50min mark into my 5am SST workouts, and I’ve been experimenting with fueling to see if i can overcome. I’m going to try increasing carbs/bottle from 90 to 100g of carbs, but I know that GI distress is a real thing and you start to flirt with that if you go too high.

1 Like

You have enough on storage to go for hours, days even weeks (depending on the energy demands).

For what it’s worth, during the earlier podcast episodes it was stated that you certainly got enough on board to go through one to two hours.

Anyway, some anecdotal evidence which perhaps explains why I asked the question I have asked:

(1) During my last Ironman I easily went through 7,500 kcal. During the swim I obviously didn’t eat at all. During the bike about 300 kcal per hour and during the run about 150 kcal per hour. The deficit easily amounted to 5,000 kcal. .

(2) When I train early I don’t have the option to prefuel my rides. So I get on the bike without having eaten for 10ish hours. Yet I am still able to get 2 to 3 hour rides in (eg Polar Bear +1). The more intense stuff (Z4+) I support with a gel or two. Though that’s only 100kcal a piece. Easy 1,500 kcal deficit right there.

(3) When I go skying with the nephews those little powerhouses hardly eat all day. You literally have to force them to sit down and eat something for lunch. Yet they are far from bonking.

Though all that doesn’t mean that fuel won’t help. Quite the opposite actually, it lowers perceived effort and generally makes things easier. However, it is still not a necessity to dose yourself in sugar on the bike. Especially not for various health reasons. For instance sake it’s super bad for your teeth and also to some extent for your organism. At least if you want to believe certain studies that indicate that sugar could play a role in cancerous diseases. I am no scientist to evaluate whether that’s sound or not. Ultimately, it doesn’t matter much. The dental aspect is already a showstopper for me.

1 Like

I got no problem with any of that. I can too go for several hour long rides with only water. But those rides take place at endurance with the occasional dip into tempo intensities. No problem.

I only use the 90g/hour if I am doing threshold work. Where it certainly lower the RPE, and make me able to better push myself at the limit. The 90 grams of carbs does not have to come from “sugar” but rather the 2:1 glucose:fructose. Personally I feel no “spikes”, and no need to raid the fridge after the ride. Dental health is a concern, so I do rinse with plain water for every swig of the “rocket fuel”. I just don’t see a lot of downsides to fuel this way, if it does indeed lower RPE, and you certainly burn the calories you take in (and more).

This is more a question than a comment:
Just because you can turn a big deficit for a long time in a race like you are saying for TRI. Does that mean it is beneficial for training? Why give the body the stress of training & energy depletion, if the goal is to come out on the other side rested and stronger?

Kind of like special forces selection. They break the candidates down to the very limit over several days. Sure some make it. But they all come out the other end weaker, needing to be “re-built”


This may be why you’re experiencing stomach pains, varying your intake with different sources of carbs and sugars along with a bit less Gatorade/maltodextrin mix may help mitigate this!

Sorry, that was poorly phrased. I meant to say that it’s not “stomach issues” that are the problem but this weird shaky/hangry reaction after the ride. That’s what I thought was weird: I assumed that GI distress would be the thing that limits carb intake, but it hasn’t been the case.

1 Like

I’ve also upped my carbs per hour to the 90-100g range. I have experience the shaky post-ride crash as well. I also have concerns about taking in a bunch of processed garbage.

For a while I was doing a combo of organic maple syrup in the bottle and shot blocks for my sugar. My blood sugar felt very unstable unless I put about 10g of protein in my bottle. This got a little expensive and I don’t think I was getting enough fructose to maximize absorption so I switched to raw organic cane sugar and organic brown rice syrup.

This has been going pretty well. I figure the brown rice syrup is essentially maltose (glucose) and cane sugar is sucrose (glucose and fructose). I shoot for 2:1. As long as I have balanced food afterward with protein and fiber I’m fine.

I thinks it’s important to use as “clean” of fuel as possible and get plenty of carbs for both the work at hand and future work. Knowing that protein and fiber stabilize blood sugar is a good guide for recovery nutrition.

1 Like