Long-distance fueling: tested protocol
On long course, fueling isn't a detail: it often separates a happy finish from a catastrophic wall at km 30 of the marathon or mid-bike on Ironman. Here's a tested protocol, simple to apply, to validate on your long runs before race day.
How many carbs per hour?
Target varies with duration and intensity, but numbers converge: 60 to 80 g/h on intense effort (marathon, end of 70.3), 70 to 100 g/h on Ironman bike, up to 120 g/h for athletes with a trained gut.
Important: the gut trains. Start at 50 g/h and ramp progressively to 90 g/h over months of long-run work. Trying to swallow 100 g/h without gut training = guaranteed vomiting.
Hydration and electrolytes
500 to 800 ml/h in temperate conditions, up to 1 L/h in heat. Without sodium, you risk hyponatremia. Target 500 to 1000 mg of sodium per liter based on your sweat (a salty sweater can go up to 1500 mg/L).
Simple test: weigh yourself before and after a 2-3h long workout. Weight loss should stay under 2% of bodyweight. Beyond that, raise hydration.
What to actually take
Reliable sources: sports drink (40-60 g/L), energy gels (25-35 g per gel), energy bars (30-40 g per bar), solid foods like banana purée. Mixing textures avoids end-of-effort disgust.
For sodium: salt capsules, electrolyte-enriched drinks, or products like Maurten 320 / SiS Beta Fuel. Test before race day: every athlete tolerates each brand differently.
- Bike: easy to eat, bars and drinks mainly
- Run: harder to digest, gels and drinks mainly
- Bike→run transition: concentrate fueling 15 min before T2 to start the run topped up
4 mistakes that cost a race
1. Trying new products on race day: absolute rule, never. Everything must have rolled across 3-4 long runs.
2. Under-fueling early: you tap reserves from hour 1, you pay at hour 4.
3. Over-fueling on the run after bike: running slows digestion. Reduce solid carbs, lean on gels and drink.
4. Forgetting sodium in heat: cramps, dizziness, even Ironman DNFs.
Build your personalized plan
Put it into practice: TriCoach AI generates a plan tailored to your level, lead time and goals.
Start for free