There's a number that decides more long-course races than VO2 max, and most serious amateurs are getting it wrong by half. It's grams of carbohydrate per hour, and the gap between what the back of the gel packet implies and what the front of a WorldTour peloton actually eats has gotten embarrassing. If you bonk at hour three of a hard effort, the problem usually isn't your engine. It's that you brought a lunchbox to a job that needed a fuel tanker.
The science here moved fast, and the old advice everyone still repeats is a decade out of date.
The number went up, and it went up a lot
For years the standard guidance was 60 grams of carbohydrate per hour, capped by how much glucose your gut can absorb through a single transporter. That cap was real — but it only applies to a single sugar. Researchers worked out that combining glucose and fructose uses two separate transporters, and suddenly the ceiling jumped. Current race nutrition built on that finding pushes elite endurance athletes to 90 grams per hour as a working floor, with some Tour de France riders documented above 120 grams an hour on the hardest mountain stages.
To put that in objects you can hold: 90 grams an hour is roughly three energy gels every sixty minutes, or two gels plus a strong drink mix. Most age-groupers I've watched are taking one gel an hour and wondering why the wheels come off. They're running a 40-gram strategy in a race that demanded 90, and no amount of base training fixes a fueling deficit.
Why you can't just double your gels tomorrow
Here's the catch nobody puts on the packaging: your gut is trainable, and right now yours probably isn't trained. Dump 90 grams an hour into a stomach that's used to 40 and you'll spend the back half of the race in the bushes, not on the bike. The intestinal transporters that move sugar into your blood actually upregulate with repeated exposure — the gut adapts like a muscle, given the same progressive overload you'd give your legs.
So gut training is a real block of work, not a race-week tweak. Practically, that means taking carbohydrate on your long sessions at close to race intensity, starting around 60 grams an hour and adding 10 every couple of weeks, until 90 sits comfortably. The brands sell this as a feature now — products like Maurten and SiS use the glucose-fructose ratio specifically so your two transporters work in parallel — but the product does nothing if your gut can't handle the volume yet.
The mistakes that cost the back half of the race
- Starting too late. If you wait until you feel hungry or flat, you're already two hundred calories in the hole and you'll never climb out mid-effort. Start fueling in the first thirty minutes, before you need it.
- Ignoring sodium when it's hot. Carbs are the engine, but in a summer race the cramping that ends your day is often a sodium and fluid problem, not a sugar one. Hit 500 to 1,000 milligrams of sodium an hour when you're sweating hard.
- Practicing a strategy you never rehearsed. Race day is the worst possible time to try a new gel brand or a higher intake. Whatever you'll do in the race, you've already done a dozen times in training.
- Forgetting that intensity changes absorption. At threshold, blood gets pulled away from the gut to the working muscles, so the same gel that sat fine on an easy ride can rebel at race pace.
Where this actually matters
None of this changes a 40-minute race. If your event is over in under ninety minutes, your muscle glycogen carries you and the carbs-per-hour conversation is mostly noise — drink to thirst and go. The fueling number earns its keep in the three-hour-plus efforts, the gran fondos and the iron-distance days and the ultras, where the body simply cannot store enough to finish and you're topping up a tank that's draining the whole time.
The pros didn't get faster at fueling because they found a secret gel. They got faster because they treated the gut as a trainable system and spent months teaching it to take 90 grams an hour without complaint. Pick your next long race that's over three hours, count the gels you've been taking, and you'll probably find the easiest free speed you've ever left on the table.