synapse800 cites 90–120g carbs per hour
- Exercise fueling — not protein timing — is the real story here. Newer endurance research has pushed the old 90 g/h ceiling toward 120 g/h in some cases. - The key number is 120 g/h from mixed carbs, not because everyone should force it, but because elite runners oxidized more fuel than at 90 g/h. - That matters because guidelines still center on 90 g/h, while newer work suggests trained guts may handle more during long, hard races.
Carb intake during endurance exercise has quietly moved from a niche sports-nutrition detail to a real performance lever. The old mental model was simple — take in some gels, avoid the bonk, call it a day. But newer work has sharpened the picture. For long, hard efforts, the question is no longer just whether to fuel. It’s how much carbohydrate per hour your gut can absorb, your muscles can use, and your race plan can actually support. Recent research tied to James Morton and colleagues is a big reason that 90–120 g/h is now a live conversation rather than bro-science. ### Where did the 90 g/h idea come from? The 90 g/h benchmark came from the shift away from single-carb drinks toward “multiple transportable carbohydrates” — usually glucose or maltodextrin plus fructose. The point is that glucose and fructose use different intestinal transport routes, so combining them lets athletes absorb and oxidize more carbohydrate than glucose alone. That’s why long-standing guidance for events beyond roughly 2.5 to 3 hours settled around up to 90 g/h, not because 90 is magic, but because it was the practical ceiling supported by older evidence. (journals.physiology.org) ### So what changed? What changed is that researchers stopped assuming 90 g/h was the hard upper limit. A 2025 Journal of Applied Physiology study in elite male marathoners compared 60, 90, and 120 g/h during 2 hours of hard treadmill running. The 120 g/h condition produced higher whole-body carbohydrate oxidation and higher exogenous carbohydrate oxidation than both 90 and 60 g/h. In plain English — more of the fuel taken in was actually getting used. (gssiweb.org) ### Did 120 g/h actually look better? Yes — metabolically, it did. Whole-body carbohydrate oxidation averaged 3.07 g/min at 120 g/h versus 2.46 g/min at 90 g/h, and exogenous oxidation in the second hour was 1.68 g/min versus 1.31 g/min. The runners also showed a lower oxygen cost of running in the 120 g/h condition, which hints at better running economy. The catch is that this was a lab study with eight elite male marathoners, not a mass-participation race field. (journals.physiology.org) ### Does that mean everyone should target 120? No — and this is where people oversimplify it. The study showed a metabolic advantage, but it did not settle that 120 g/h is automatically the best performance target for every runner, cyclist, or triathlete. Even the paper itself flags that the performance implications still need to be nailed down. Basically, 120 g/h looks possible and useful for some athletes, but it is not a universal commandment. (journals.physiology.org) ### What’s the limiting factor? Usually the gut. At 120 g/h, nausea, stomach fullness, and abdominal cramping were worse than at lower doses, even though severe symptoms were not universal. That’s why “gut training” keeps coming up. Your intestine is a bit like a feed chute — if you never practice race-day intake in training, shoving 3 or 4 gels’ worth of carbs per hour into it on race day can backfire fast. (journals.physiology.org) ### Why do people mention recovery too? Because carbohydrate during exercise is partly about protecting what you have left afterward. A 2020 mountain-marathon trial found that 120 g/h, compared with 90 and 60 g/h, lowered internal exercise load and reduced markers tied to exercise-induced muscle damage 24 hours later in elite runners who had already practiced nutritional gut training. That does not mean carbs replace recovery nutrition. It means better fueling during the effort can leave less wreckage to clean up later. (journals.physiology.org) ### What should a normal endurance athlete do with this? Treat 90 g/h as a proven anchor, not a ceiling you must smash. If your event is long and intense, mixed carbs matter more than heroic single-gel bursts. If you want to experiment above 90 g/h, do it in training, with a repeatable product mix, and with enough time to learn what your gut tolerates. The science is moving toward “personalized fueling,” not “everyone slam 120.” (pmc.ncbi.nlm.nih.gov) ### Bottom line The real update is not that 120 g/h has replaced 90 g/h. It’s that the old 90 g/h ceiling now looks more like a strong default — and for some well-trained athletes, not the limit. (fisiologiadelejercicio.com) (isenc.co.uk)
