Ironman Distance Triathlon Fueling Guide


Fueling for an Ironman (2.4-mile swim, 112-mile bike, 26.2-mile run) is critical for success. A practiced nutrition plan sustains energy, prevents bonking, and aids recovery. Below are key strategies based on expert and athlete insights.


Pre-Race Fueling

Carb Loading (4-7 Days Out): Gradually increase carbohydrate intake to 8-12g/kg body weight daily to maximize glycogen stores. Focus on complex carbs like rice, pasta, or oats. Example: A 70kg 155lb athlete needs 560-840g carbs/day.
Practice in Training: Test race-day nutrition (gels, bars, chews, drinks) during long training sessions to train your gut and confirm what works. Avoid new foods on race day.
Night Before: Eat a familiar, carb-rich meal (e.g., pasta with lean protein, low-fat sauce). Avoid high-fiber or fatty foods to prevent GI distress.
Race Morning (2-3 Hours Before): Consume 1-2g carbs/kg body weight (e.g., oatmeal, toast, banana, or sports drink for a 70kg athlete: 70-140g carbs). Sip water or an electrolyte drink to stay hydrated.


Race-Day Fueling


General Guidelines


Carbohydrates: Aim for 60-90g carbs/hour (up to 120g/hour for advanced athletes using hydrogel products like Maurten). Use a mix of gels, chews, bars, or sports drinks.
Hydration: Drink 500-750ml/hour, adjusting for sweat rate and weather conditions. Include 500-1000mg sodium/hour via electrolyte drinks or salt tablets. Tools like Precision Fuel & Hydration’s free Fuel & Hydration Planner can personalize this.
Timing: Start fueling early (within 10-15 minutes on the bike) and consume small amounts every 20-30 minutes to maintain steady energy.


By Discipline


Swim (2.4 miles, ~1-2 hours): Fueling is minimal due to logistics. If possible, sip a carb-electrolyte drink 10-15 minutes before the start.

T1
Bike (112 miles, ~5-7 hours): Primary fueling phase. Consume 60-90g carbs/hour (e.g., 2 gels at 25g carbs each + 500ml sports drink at 20g carbs). Sip water or electrolyte drink every 10-15 minutes. Example: 1 gel every 20 minutes + 1 bottle/hour.
special needs bag
T2

Run (26.2 miles, ~3-5 hours): Maintain 30-60g carbs/hour via gels, chews, or drinks, as GI distress is more common. Rely on aid stations or carry a concentrated carb drink. Sip water and electrolytes to replace sweat losses.
special needs bag

Post-Race Recovery


Immediate (0-30 minutes): Consume 1-1.2g carbs/kg body weight + 20-25g protein (e.g., a recovery shake with milk, banana, and protein powder for a 70kg athlete: 70-84g carbs).
Within 2 Hours: Eat a balanced meal with carbs, protein, and moderate fats (e.g., rice, chicken, vegetables).
Hydration: Rehydrate with electrolyte-rich fluids until urine is pale yellow.


Tips from Athletes and Coaches
Alice Alberts (Pro Triathlete): “Fueling is a discipline. Train your gut like you train your swim, bike, and run.”
Emma Yates (Age-Grouper, Ironman Wales): Used a mix of gels and sports drinks, adjusting based on course demands (e.g., hills) and aid station availability.
Rebekah Keat (Coach): Start carb loading 4 days out. Test liquid vs. solid fuels in training to find your preference.


Common Pitfalls to Avoid
Under-Fueling: Leads to bonking (glycogen depletion). Set a timer to eat/drink every 20-30 minutes.
Over-Fueling: Causes GI distress. Stick to practiced amounts and avoid overconsuming at aid stations.
Ignoring Sodium: Low sodium can cause cramps or hyponatremia. Test sweat rate and sodium needs in training (e.g., via sweat tests or Precision Fuel & Hydration).

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