Carbs At 90g Per Hour And Blood Sugar Crash

So I’ve been riding for many years as a weekend warrior type, and most of my rides have been fueled by a couple of bananas, a bagel or two, and whatever can be gathered at various stops along the way. A couple of years ago, I started structured training with TR, and my nutrition strategy was to keep doing what “worked” for me: Usually didn’t eat anything on the bike, and normal meals without a major increase in calories consumed. (“Hey look at all the weight I’m losing!” just before everything falls apart in week 2 of the build phase)

Anyway, I’ve started experimenting with really taking on carbs during workouts, and I’m doing about 90g an hour of Gatorade/maltodextrin mix. One thing I’ve noticed is that, while I’ve managed to keep just this side of stomach issues, I’ve been experiencing some pretty unpleasant post-workout side-effects that seem related to blood sugar (shakiness, sweaty palms, etc…) that seem to get resolved by, say, eating everything in the fridge as fast as possible.

I don’t have this reaction after some 90 min 1300kcal threshold workout if I just eat a banana beforehand and drink water. Is this something others have experienced, or is this a “run immediately to your doctor” things?


I think even 90g might not cover what you burn. Each gram should give you 4 calories (360 calories / hour) - at least according to my very superficial research. This means you still have a deficit of 700-800 calories after 90 minutes. Most of the energy comes from the carbs stored in your muscels and if you go into the workout more or less empty you still could run dry…

This is not medical advice and talking to a doctor is probably still a good idea.

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Do you have a medical condition that would make you think your having problems controlling your blood sugar? What are you eating when you get off the bike?

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Yeah, that’s the weird thing: I don’t get these “crash” symptoms unless I flood my system with sugars. I’ve had yearly blood work, checkups, etc, etc… and never had any condition detected. Like I said, it’s only recently that I’ve started trying to consume a lot of carbs during rides/workouts. I’ve had similar issues in the past (used to try to eat a cliff bar every 15-30 min or so, and occasionally suffered this kind of “bonk”), but don’t remember it ever happening when I’d just eat bananas, bagels, etc… which, to be sure, was significantly underfueling…

Right, like I said if I eat some oatmeal in the morning, then do a 1200kcal ride on nothing but water, I don’t get the same symptoms. (I might lose steam in the workout, or might feel hungry an hour or so later, or whatever, but I don’t get the sweaty palms, panicked feeling). I had a full blood workup about 3-4 months ago, but I don’t know whether that includes any insulin-related testing or whatever.

I’ve reached out to my PC, but my guess is that (like most TR-related issues) they’ll respond with a “well, stop doing that then.” :slight_smile:

If you have no medical conditions I would suggest a couple things:

  1. Cut back to how much you are taking on during the ride
  2. Have a light amount of fibery carbs before the ride; banana, apple, whatever
  3. Have a recovery meal after with some carbs and protein; recovery drink, peanut butter toast

Not anything that’s been detected with yearly physicals, a full blood workup four months ago, etc… Like I said, it’s something I seem to remember happening in the past when I’ve tried to fuel with a lot of ride-specific food sources (gels, bars, mixes, etc…). Just wondering if anyone else has that kind of sensitivity to sugars, or if it’s a yellow flag…

I’ll occasionally get the same symptoms after a long ride, but it has to be a ride that’s longer than what I’ve been doing recently, and it’s usually the opposite issue where I can point to an under-fueling issue. Does this happen with different fuels? What is the ride duration when this happens?

Ride specific fuel has almost always worked well for me, and it’s when I take the advice of “all sugar is the same” and eat something super sugary like a candy bar in place of a gel that I will peak and crash from that. If I eat a lot of white rice before a ride, or a lot of white bread, apples - these all seem to give me terrible results so I’ll avoid those for lunch when I’m planning an afternoon/evening ride. Almost always leaves me feeling like I’m going to bonk then I’m grabbing for a gel well before I think I should need to.

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Maybe an allergy? Did you ever try 90g of specific food without a workout? This could help narrow it down…

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Thanks, good to hear I’m not the only one. Maybe it’s a matter of too much too soon, but from following some of the discussions here in the TR forum, podcasts, etc… I had assumed the limiter was GI discomfort, not insulin regulation… lol

I used to just do a banana and/or gel during rides but following the making SIS Beta fuel thread I have just started with maltodextrin and instead of jumping in the deep end decided that I’d start around 40g/hr. So far touch wood its going ok - maybe try cutting back from 90 and start lower. I though 60g was accepted as a good starting point?
Just a thought but if it keeps happening I’d be seeking the advice of a doctor or dietitian maybe.

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Good advice–I’m starting to think maybe I was flying too close to the sun. It’s funny, I made a mature, conscious decision to lower my FTP for this training block because I test high, so I guess my over-enthusiasm had to find its expression elsewhere…


It seems like you went from 0 to a maximal amount very quickly. People talk about training their gut to process this much carb. Are you trying 90g of carb on every ride?

Personally, I think you should go back to oatmeal and bananas for most rides. Maybe try sugar doping for intervals or races only. Another thing to consider is that 90g of sugar per hour of riding can be hard on your teeth.

For a 4-5 hour gravel ride, I would bring a couple of bananas, a Cliff bar, and a couple of peanut butter sandwiches. I’d also have a big breakfast ahead of time (oatmeal + eggs). Some fat, a little protein, and low glycemic carbs seem to give me great all day energy.

If you really want the sugar for an event, there are products like UCAN that are slow release and have a lower glycemic index.


You might be right. I guess the two questions I have are:

a) What are the symptoms of exceeding your (trained or untrained) maximal carb uptake? Everything I’ve read seems to imply the penalty is gastric distress, not some kind of hypoglycemic episode.

b) Whether other (non-diabetic) people have experience similar hypoglycemic symptoms and at what level of simple carb consumption.

Wouldn’t this be a hyperglycemic response?

Per Mr. Google, one of the symptoms of hyperglecmia is hunger or thirst.

Hmm. I’m not seeing hunger anywhere:

Sounds to me the result of low blood sugar possibly caused by an exaggerated insulin response to the high carbohydrate load. Usually during muscular exercise of any intensity insulin is not elevated and the working muscles can take up carbohydrate in the absence of insulin. You might ask your PC to check fasting insulin levels. If elevated may need to be addressed.

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Thanks, this is good advice!

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Do you really need that much sugar to get the workouts done? Assuming you get on the bike in a fairly topped up state (eg normal meal some hours beforehand) you shouldn’t have much problems completing a 90 minute threshold session.

I know this is an unpopular opinion here but to my experience most of the workouts can be done with not much more than some coffee and perhaps a gel or block. After all, most of them are somewhere between 60 and 120 minutes.

Either way, I would definitely also consult a doc to make sure everything is all good.


That’s the way I’ve done things in the past, but I’ve had a tendency to burn out (mentally and physically) around halfway through Build. That’s what precipitated this experiment with less volume and more fuel.