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Running
Hitting the wall is not a willpower event. It is running out of stored carbohydrate, on a schedule you could have predicted and prevented.
Under 60 minutes: nothing needed. 60–150 minutes: 30–60 g of carbohydrate per hour. Over 150 minutes: 60–90 g per hour, which requires a glucose-plus-fructose mix. Start fuelling before you need it, at around 30–40 minutes.
Muscle and liver glycogen hold roughly 90–120 minutes of running at a decent pace. Fat supplies the rest, but not fast enough to sustain the effort, which is why the pace falls off a cliff rather than easing down gently. Taking carbohydrate in spares the stored supply and pushes the cliff past the finish.
| Run length | Carbs per hour | Practical form |
|---|---|---|
| Under 60 min | 0 | Water if warm |
| 60–90 min | 30 g | 1 gel, or 500 ml sports drink |
| 90–150 min | 30–60 g | 1 gel every 30–40 min |
| 150–180 min | 60–90 g | Glucose + fructose products |
| Over 180 min | 60–90 g | Mixed sources; include some real food |
The 60 g ceiling exists because glucose transport across the gut saturates around there. Getting beyond it requires fructose alongside glucose, which uses a separate transporter — which is why products marketed at 2:1 or 1:0.8 ratios exist and why plain glucose gels stop scaling.
| Time before | What | Amount |
|---|---|---|
| 3–4 h | Normal carb-based meal, low fat and fibre | 1–3 g carb per kg |
| 1–2 h | Light snack: banana, toast and honey, rice cakes | ~30–60 g carb |
| 15 min | Optional gel for a very long run | ~25 g |
Early morning runs are the awkward case. For anything up to about 90 minutes, running fasted is fine if you are used to it. Beyond that, something is better than nothing — even a banana and a sports drink twenty minutes before changes the back half.
The capacity to absorb 90 g of carbohydrate an hour while running is trainable, and it is not present by default. Attempting race-day fuelling for the first time on race day is the origin of most endurance stomach disasters.
Within an hour: 1–1.2 g of carbohydrate per kg and 25–40 g of protein. Then a real meal. Recovery from a long run is mostly a carbohydrate problem, and under-eating afterwards is the most common reason the following week’s sessions feel flat.
Nothing under 60 minutes. Between 60 and 150 minutes, 30 to 60 grams of carbohydrate per hour. Beyond 150 minutes, 60 to 90 grams per hour, which requires products combining glucose and fructose because glucose absorption alone saturates around 60 grams.
Start at around 30 to 40 minutes, before you feel you need it, and then every 30 to 40 minutes after that. Waiting until you feel depleted means the carbohydrate arrives too late to prevent the drop in pace.
A carbohydrate-based meal low in fat and fibre three to four hours beforehand, at one to three grams of carbohydrate per kilogram of bodyweight, plus a light snack such as a banana or toast one to two hours out.
Train your gut gradually: start at 30 grams of carbohydrate per hour, add about 15 grams every couple of weeks, and always use the exact products you plan to race with. Take carbohydrate with water and avoid high fat and fibre in the hours beforehand.
Gut training only works if you record what you actually took and how it went. NutriMacro logs the run by GPS and the carbohydrate you took alongside it, so the progression from 30 to 90 grams an hour is a plan rather than a guess.
NutriMacro is a nutrition and training tracker for iPhone and Android. It logs food by barcode, photo or search, counts food in slices and units rather than grams, and keeps strength training, GPS activities, sleep and recovery in the same daily view. It runs in the language of your phone across 108 countries.
General guidance for healthy adults, not medical advice. Practise all race fuelling in training; gut tolerance is highly individual and trainable.
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