Introduction
The most important revolution in sports nutrition over the past decade has been “high-carbohydrate fueling.” From the early 60g/hr, it has now increased to 90-120g/hr, with elite athletes reaching up to 150g/hr. This article teaches you how to train your gut, choose sources, and execute this strategy in an IRONMAN.
Why Do You Need This Much Carbohydrate?
- Glycogen stores: approximately 400-500g (1600-2000 kcal)
- IRONMAN expenditure: 8000-12000 kcal
- External fueling needed: 4500-8000 kcal (approximately 1500-2000g of carbs)
- 90g per hour = 360 kcal × 10 hr = 3600 kcal
Carbohydrate Source Combinations
Key: glucose + fructose = 1:0.8 ratio can significantly improve absorption rates.
| Source | Carb Amount | Ratio |
|---|---|---|
| Maurten 320 (500ml) | 80g | 1:0.8 |
| Maurten Gel 100 | 25g | 1:0.8 |
| Precision Hydration PF90 | 90g | 1:0.8 |
| Standard energy gel | 20-30g | Mostly glucose |
| Medium banana | 25g | Glucose |
| Coke 250ml | 28g | Glucose + fructose |
Gut Training
The gastrointestinal tract is a trainable organ, requiring 8-12 weeks of gradual progression:
- W1-W2: 60g/hr long ride
- W3-W4: 75g/hr long ride
- W5-W6: 90g/hr long ride
- W7-W8: 105g/hr long brick
- W9-W10: 120g/hr race-sim
Three-Phase Race-Day Fueling
| Phase | Carbs per Hour | Primary Sources |
|---|---|---|
| Bike 0-90km | 90-120g | Maurten drink + gel |
| Bike 90-180km | 80-100g | gel + banana + salt tablets |
| Run 0-21km | 60-80g | gel + sports drink at aid stations |
| Run 21-42.2km | 40-60g | Coke + broth + watermelon |
Practical Tips
- Do 1 “fueling rehearsal” long ride per week, accurately recording grams
- Never try a new product for the first time on race day
- In hot conditions, prioritize liquids; in cold conditions, solids are fine
- Carry 1-2 “emergency gels” in case you miss an aid station
- If your stomach feels bloated, switch to cold Coke or watermelon
Conclusion
“Those who can fuel win; those who can digest finish” is the golden rule of IRONMAN fueling. Gut training doesn’t require willpower—it requires 8-12 weeks of patient accumulation. Treat it as part of your physical training, and you’ll find you still have sprinting room left in the second half.
Related Reading
- 70.3 Fueling Strategy: The Science and Practice of 60–90g of Carbs Per Hour
- Fueling Strategy in Training: How to Achieve 60–90g of Carbohydrates Per Hour
- The Science of Fueling During Exercise: How Many Carbs Per Hour Should You Eat? A Complete Practical Guide from 60g to 90g
- Ironman Full-Distance Nutrition Plan: A Complete Guide to Hour-by-Hour Fueling Strategy
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