Race-Day Fuelling phase
Race-Day Fuelling One-Pager
Every gram, millilitre and milligram on one sheet, from the published ACSM and Jeukendrup guidelines. Print it, tape it to your top tube.
The rules
- For anything over an hour, take 30 to 60 g of carbohydrate per hour. A single source such as glucose or maltodextrin is absorbed effectively up to about 60 g/h.
- To go above 60 g/h on long races, you need multiple transportable carbohydrates, a glucose-to-fructose blend, and a gut trained to absorb them.
- Drink 400 to 800 ml of fluid per hour: the higher end for heavier, faster athletes in the heat, the lower end for lighter, slower athletes in the cool.
- Once you are past an hour, include 500 to 700 mg of sodium per litre of fluid.
- Practise your exact race-day intake in training. Race day is not the place to test a new gel, bottle or number.
Fuelling targets by race duration
| Race (typical duration) | Carbs per hour | Fluid per hour | Sodium |
|---|---|---|---|
| Sprint | 30 to 60 g | 400 to 800 ml | 500 to 700 mg/L |
| Olympic | 30 to 60 g | 400 to 800 ml | 500 to 700 mg/L |
| Half Ironman | 60 to 90 g (glucose + fructose) | 400 to 800 ml | 500 to 700 mg/L |
| Full Ironman | 60 to 90 g (glucose + fructose) | 400 to 800 ml | 500 to 700 mg/L |
Keep / drop
Keep
- The carb number your gut has actually practised
- A glucose-plus-fructose blend for anything over 2.5 hours
- Sodium in the bottle, not just salt tabs you forget to take
- The same breakfast and pre-start fuel you rehearsed
- A per-hour plan on a timer, decided before the gun
Drop
- A brand-new gel or drink you have never trained with
- Chasing 90 g/h on an untrained gut
- Waiting until you feel empty to start eating
- Plain water only on a hot, long race
- Copying a faster athlete's numbers without testing your own
The session menu
- Before the start
- Top up with a familiar carb-rich meal 3 to 4 hours out, then a small top-up shortly before. Nothing new on the morning.
- On the bike
- The easiest place to eat. Take the bulk of your hourly carbs here, on a timer rather than by feel.
- On the run
- Harder to digest. Lean on liquids and gels and hold the carb rate you set on the bike, sipping to your plan.
- After the finish
- Start eating within the first hour: carbohydrate to refill the tank and protein to repair. Rehydrate with sodium, not plain water alone.
Red flags
- Sloshing stomach, nausea or cramps: you are taking on more carb or fluid than your gut can absorb at that intensity. Back the rate off.
- Swollen fingers, a headache, or feeling worse the more plain water you drink: signs of over-drinking and low sodium. Add electrolytes and stop forcing fluid.
- Going suddenly hollow with heavy legs late on: you fuelled too little or too late. It is very hard to claw back once you are empty.
- You are guessing your intake mid-race. The plan should be a number per hour on a timer, set before the start.
Next step
Turn these ranges into your own per-hour numbers for your race distance, weight and expected finish time.
Race Nutrition PlannerSources
Important
These are general ranges from published sport-nutrition guidelines, not personal medical or dietary advice. Sweat rate, sweat sodium and gut tolerance vary widely between athletes, so test every number in training and adjust to your own tolerances. If you have a medical condition or take medication, talk to a doctor or a registered sports dietitian before changing your race-day intake.
Condensed from the full Ironman Guide. mytriathloncalculator.com
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