Gut training: building the carbs-per-hour ladder across a block
You can train your stomach the way you train your legs — progressively, on named sessions, with a number you climb. Here is how to build the ladder, where the ceilings are, and what to do when a rehearsal goes badly.
Most people who blow up late in a marathon did not run too fast. They ran a pace their legs could hold on fuel their stomach could not take.
The fix is not a gel brand. It is that the gut is trainable, and almost nobody trains it — they read that elites take 90–120 g of carbohydrate an hour, try it on race morning having practised at 30, and spend the last 10 km looking for a portaloo.
This is how to build the ladder instead.
The number that matters is per hour
Fuelling during a long session is measured in grams of carbohydrate per hour, not per gel and not per kilogram of you. Absolute units are the right frame for gut training specifically: 30 → 60 → 90 g/h is the same ladder whatever you weigh, because what is being trained is the intestine's capacity to absorb, not an energy balance.
Roughly where the rungs sit:
| Rung | g/h | Who is here |
|---|---|---|
| 30 | 30 | Most people who have never thought about it |
| 60 | 60 | A trained gut on a single carbohydrate source |
| 90 | 90 | Needs glucose + fructose together, and practice |
| 100–120 | 100+ | Well-trained guts, long course, deliberately built |
Above about 60 g/h the limit stops being your stomach and becomes transport: glucose saturates one pathway, so the extra has to arrive as fructose using another. That is why a 90 g/h product usually says 2:1 or 1:0.8 on the packet. It is not marketing.
Climb it across the block, not on race week
The ladder is a training progression, so it belongs on the plan the same way volume does.
A workable shape for a marathon block:
- Weeks 1–4 — 30–40 g/h on the long run. You are establishing the habit of eating while running at all.
- Weeks 5–9 — 50–60 g/h. Start splitting sources if you have not.
- Weeks 10–14 — 70–90 g/h on the two or three longest sessions, at race intensity for part of them.
- Taper — no new rungs. You are confirming, not testing.
Two rules that do most of the work:
Rehearse at race intensity, not just race duration. A gut that copes at easy pace can fail at marathon pace, because blood goes to the legs. At least two rehearsals should include a block at goal effort.
Rehearse with race products. If the course hands out one brand, practise with that brand. The most common avoidable disaster is meeting a new formulation for the first time at 30 km.
Fluid and sodium ride along
Carbohydrate is the headline, but the other two matter and are more individual.
Fluid follows sweat rate, which you can measure crudely: weigh yourself before and after an hour of running in the conditions you expect, and the difference plus what you drank is roughly your hourly loss. Most people land between 400 and 1000 ml/h; heat pushes it up sharply.
Sodium follows how salty a sweater you are — the white crust on your cap is a real signal. Typical ranges run 300–1000 mg per litre of sweat, and long, hot events are where getting it wrong shows up.
Neither is a number to guess once and forget. Both change with heat, and both should be rehearsed alongside the carbohydrate.
When a rehearsal goes badly
This is the part people skip, and it is the whole point of rehearsing.
If a session leaves you heavy, queasy or stopped, do not push to the next rung. Hold where you are, or step back one, and repeat. A gut that failed at 75 g/h will not succeed at 90 because the calendar says week 12. The ladder is driven by what your stomach did last time, not by the plan you wrote in January.
Write down what happened — the rate, the products, the conditions, and how it felt. Three rehearsals in, that record is the most useful fuelling data you own, and it is specific to you in a way no article can be.
Where this stops
Gut training is a training protocol, not a diet. Intake during a session, the ladder, race-day rate, and a practical carb load in the last days before a race — that is the scope.
It is deliberately not meal plans, not calorie targets, not macro splits, and nothing about body weight or composition. Those are different questions, several of them are questions for a professional, and blending them into a fuelling plan is how a training tool turns into something it has no business being.
If eating around training has become a source of anxiety rather than a logistics problem, that is worth talking to a sports dietitian about, and it is worth doing before the next block rather than after it.
How Stopa does it
In Stopa the ladder is an overlay on the plan you already have: a rate per hour on the sessions that carry one, rehearsals marked on named long runs, race day and the carb-load days stated, and a reminder the evening before a rehearsal so you buy the gels.
Afterwards it asks one question — how the stomach handled it — and the answer moves the ladder. A bad report holds or steps back a rung rather than climbing on schedule. Everything is in absolute g/h, ml/h and mg/h, with hard ceilings, because a fuelling number that is wrong in the wrong direction is not a rounding error.
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- Apple Watch WorkoutKit, explained honestly
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