How do I avoid nausea late in the race?
Late-race nausea comes most often from too high a sugar concentration in a gut whose blood supply has dropped. Diluting more, switching to savoury and liquid, and splitting intake into smaller, more frequent feeds solves most cases.
During effort, blood is redirected towards muscles and skin at the expense of the digestive system. The gut still receives what you send it, but absorbs it more slowly. A drink that is too concentrated then sits there, pulls water in from the body by osmosis, and that distension triggers the nausea. The problem is not the total amount of sugar, but its concentration at a given moment.
This is why drinking plain water on top of an over-sweet drink rarely makes things worse and often improves them: it brings the concentration back into an absorbable range. Conversely, the classic mistake is to answer nausea by stopping eating altogether — which fixes the symptom for an hour, then produces a bonk you do not come back from.
On a real race: Mont-Blanc — UTMB®
On Mont-Blanc — UTMB®, a runner with an Index of 600 spends about 20 hours in darkness out of 37h10 on course. That is the critical window: appetite falls, alertness drops, and the low point usually sits between 3 and 5 a.m. Planning savoury, warm and liquid food for that moment beats discovering at 4 a.m. that you cannot face another gel.
| UTMB® Index | Estimated time | Carbs | Fluid | Sodium |
|---|---|---|---|---|
| 500 | 43h01 | 2,581 g | 30.1 L | 21,508 mg |
| 600 | 37h10 | 2,230 g | 26 L | 18,583 mg |
| 800 | 24h36 | 1,476 g | 17.2 L | 12,300 mg |
Temps repris des passages réels des coureurs de chaque tranche de cote sur les éditions précédentes, arrêts aux ravitaillements compris. Besoins calculés à 60 g/h de glucides, 700 mL/h de liquide et 500 mg/h de sodium, par temps tempéré.
In practice: lower the concentration rather than the quantity, alternate flavours from one station to the next, keep a savoury option — broth, soup, crisps — for the second half, and split your feeds. If nausea sets in anyway, ease off for ten minutes: dropping the intensity returns blood flow to the gut and often lets you get going again.
RAVIT applies this calculation to 2,778 races across 49 countries, with 6,547 aid stations whose contents are taken from the official rulebooks.