How Much Carbohydrate Per Hour? Ultracycling vs. Long-Course Triathlon
In the world of long-distance cycling, the list of decisive aspects gets longer the longer the event lasts. It starts with building an excellent physical base in endurance — without neglecting the need to tolerate the increasing force on passive structures through higher torque, hike-a-bike sections, and merely the sheer length of an event that can last anywhere from many hours to many days. Aside from the training side, there are plenty of other aspects: logistical challenges from route planning to packing to mechanical skills, and so on. And bike-fitting issues, and even aerodynamics. But one of the biggest parts is still sometimes overlooked across all the different distances and training approaches, and I’d like to borrow a term from aerodynamics — “free speed”: it’s nutrition. You can damage your training effect as well as boost it, and on race day(s) it’s the most crucial part of using your built form to the fullest extent.
Few topics in endurance sport stir up as much debate as the “right” carbohydrate intake. Ever since a handful of WorldTour pros started talking publicly about 120 g/h and beyond, more has quietly become synonymous with better. Look at the evidence soberly, though, and a more nuanced picture emerges: on the long, steady demands of ultracycling, intakes above 90 g/h largely lack evidence and deliver no measurable advantage. In long-course triathlon, by contrast, going higher can make real sense — for entirely different reasons.
In this article
Why ~90 g/h covers the moderate carbohydrate burn of long, steady ultracycling.
The transporter physiology behind the ~60 g/h glucose ceiling — and how a glucose-plus-fructose blend lifts it.
Why intakes above 90 g/h show little performance or glycogen-sparing benefit on the bike.
How long-course triathlon flips the math: the run, the gut depot, and trained fructose tolerance.
Why relative intensity — your fractional VO₂max — sets your real carbohydrate demand more than the discipline does.
The practical rule: match the dose to the demand, not to the headlines.
A Quick Word on the Physiology
The bottleneck doesn’t sit in the stomach or even the gut itself, but in the transporters. Glucose (and maltodextrin, which — although it is a longer chain of glucose molecules — behaves like glucose) is absorbed via the SGLT1 transporter, which saturates at roughly 1 g/min — about 60 g/h, give or take a few grams, and excluding the tails of a Gaussian distribution and highly adapted individuals. Drinking more pure glucose beyond that point doesn’t increase the amount you oxidize; the surplus just sits in your gut. To go higher, you need a second channel: GLUT5 transports fructose independently of SGLT1. Combine glucose and fructose, and exogenous oxidation rates well above 1 g/min become possible — up to around 1.26 g/min in studies (Jentjens et al., 2004).
Two points here are routinely overlooked:
The transporters aren’t fully saturated until roughly 90–120 minutes into a session. Before that, the carb blend barely matters — and under two hours, even total quantity is secondary.
The highest oxidation ratio (around 0.8:1 to 1:1 fructose-to-glucose) produces the maximal rate, but it also leaves the largest residual amounts in the gut. That residual is precisely what becomes the central problem over very long distances.
Keep both of these in mind — the entire ultracycling-versus-triathlon argument turns on them.
Ultracycling: Why More Usually Isn’t More
In classic ultracycling — hours, sometimes days, at an intensity well below critical power (CP) or maximal lactate steady state (MLSS) — your real carbohydrate burn is moderate. At these intensities it often sits in the 40–70 g/h range. An intake of 60–90 g/h, paired with your own stores, covers that comfortably. There simply isn’t a metabolic demand that justifies going higher. It’s more reasonable to consider a kind of carb-cycling approach: fuel constantly with a baseline, and go higher (above 60 g/h, for example) when your intensity increases (climbs, etc.). Or, if you’re a high-performance athlete, fuel high-carb as long as you can hold relative intensity high, and go lower when fatigue kicks in — before you restart after resting/sleeping, or simply after overcoming the fatigue phase.
The research backs up this restraint. Wilson’s 2025 review, which specifically pitted studies using 100 g/h or more against the established 60–90 g/h, found no clear evidence that the higher intakes improve performance. At best there are weak hints of a minimal, statistically significant glycogen sparing. Crucially, on the bike those higher exogenous oxidation rates don’t translate into reduced use of your own stores — the hoped-for “sparing effect” largely fails to materialize. (One exception: adequate intake can leave liver glycogen almost entirely untouched, which is a genuine benefit — but that already happens at much lower doses.)
Then there’s the downside of high doses. Concentrations above roughly 10% — more than 100 g per litre — actually slow gastric emptying and lower the oxidation rate. When you exceed the transport capacity of SGLT1 and GLUT5, the unabsorbed sugars pull water into the small intestine and ramp up fermentation. The result is distension, bloating, and nausea (Rehrer et al., 1992). Exercise makes it worse, because blood flow to the gut drops and absorptive capacity suffers (Costa et al., 2017). Over 6, 12, or more hours, that adds up fast.
For long, steady cycling, then, the smart strategy is the opposite of “max everything”:
Medium carb load, low fructose ratio — maximal oxidation with the smallest possible residual.
High fructose is optional, not mandatory. You don’t have to use it. If you tolerate it well, you may — but there’s no obligation.
Where high doses do earn their place in cycling in general is as a logistical problem-solver. In multi-day stage races, the goal is to offset a massive energy deficit that would be nearly impossible to cover off the bike. Here the high intake serves your energy balance and recovery — not your in-the-moment performance. Aside from that, being more “carb-dependent” may help raise intensities at the end of stages. But that is definitely more relevant to classic road-race and stage-race scenarios.
Long-Course Triathlon: The Run Changes Everything
In long-course triathlon, the math flips — and the reason is the marathon waiting at the end.
During cycling, external carbohydrate barely spares muscle glycogen. But if you’re oxidizing carbohydrate maximally on the bike and staging a reservoir, you enter the run with a better starting position.
This is where the gut residual — a disadvantage in ultracycling — becomes a potential asset: a depot that delivers carbs during the run. So carbs trickle in from that depot, and the usually lower carb doses in running keep coming on top. Since very high carb doses are often not tolerated that well (due to oscillation or lack of training), you have more matches to burn now. The catch is that you have to tolerate those amounts — and that’s the whole point:
In ultracycling you can avoid high-fructose/high-carb amounts.
In long-course triathlon you have to be able to handle it if you genuinely want to push the oxidation rate to its ceiling.
The race duration also works in your favour here. It’s measured in hours, not days, so the larger residual matters less — and it supports the metabolic handover into the run.
The Real Lever: Power Output
Here’s the part that’s easy to miss: the decisive variable isn’t solely the discipline — it’s relative intensity.
Carbohydrate is the dominant fuel the moment things get hard, and the higher your power, the exponentially higher your carb turnover. The crossover point illustrates this neatly. As a session drags on, fat oxidation normally takes over a bigger share. A high carbohydrate intake pushes that point further out — 90 g/h delays it substantially, and very high intakes can prevent the crossover from happening at all across a three-hour effort. That matters because keeping carbohydrate available preserves your ability to surge into hard intensity zones at any moment (note the stage-race example above), and because fat oxidation dominating too early goes hand in hand with fading power late in the race (the durability factor; cf. Ortenblad et al., 2024).
In augo: how one athlete’s carbohydrate intake ramped through the spring as training load and intensity climbed.
Which leads to the essential caveat:
High doses with a high fructose ratio only pay off when carbohydrate turnover is genuinely high — that is, at a relatively high percentage of your own VO₂max.
An athlete racing long-course at a high fractional utilization has a correspondingly high carb demand that maximal oxidation can feed (the more so, the higher the absolute VO₂max). That’s where the likely advantage lives — and, fittingly, the benefit of very high intakes is reported mostly anecdotally among elites, far less among moderately trained athletes.
For less powerful athletes, the picture reverses entirely. Tackle the same race at a much lower absolute and relative intensity, and your carbohydrate turnover is far lower. You never come close to maxing out oxidation, the crossover point is less critical, and considerably less is enough. Pushing big quantities with an aggressive fructose ratio would mostly hand you the downsides (GI risk, the training burden of conditioning your gut) without the matching upside.
The Takeaway
The question “90 g/h or more?” has no one-size-fits-all answer — it depends on the demand.
Ultracycling, long and moderate, gives you little performance reason to exceed 90 g/h. Prioritize a well-tolerated, low-residual supply; high fructose is optional, not necessary. The main justification for big doses is energy balance in multi-day racing.
Long-course triathlon is where going higher can genuinely make sense. The run that follows makes a maximal oxidation rate and a staged gut depot valuable — which is exactly why you need to train yourself to tolerate the fructose that’s required.
But even that comes with a firm condition: it only pays off at a high fractional VO₂max utilization and the high carb turnover that comes with it. Race slower, and you’ll do just as well — and usually more comfortably — on far less.
Match the dose to the demand, not to the headlines.
About the author
Max Kinzlbauer is a cycling coach based in Neumarkt/Wallersee, Austria, and the founder of MAX Training. He coaches ultracycling (supported and unsupported), gravel, and road athletes, with a particular focus on training methodology and periodization, race-day nutrition, and heat adaptation.
Max is an augo founding coach — one of the coaches who has been building augo with us since day one, helping shape the platform from the very beginning.
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