Bike Segment Fueling Rhythm: 90 g/hr Dual-Source Carbohydrate (Glucose + Fructose) Formula

Why 90 g/hr Is the New Standard

The biggest breakthrough in sports nutrition over the past decade: dual-source carbohydrates pushed the hourly carbohydrate absorption ceiling from 60 g to 90–120 g.

Physiological principle:

• Glucose uses the SGLT1 channel, ceiling ~60 g/hr
• Fructose uses the GLUT5 channel, an independent pathway, ceiling ~30 g/hr
• Using both together = 90 g/hr total absorption

The Science of the 2:1 Ratio

Glucose:fructose = 2:1 is the ratio with the highest gastrointestinal tolerance + best absorption efficiency in research.

Example: 60 g glucose + 30 g fructose = 90 g total carbohydrates

A Specific 90 g/hr Formula (DIY Version)

Formula A: Liquid-Based (Ideal for Hot Weather)

Make 1 L of sports drink:

How to drink: Finish 1 L per hour = 90 g carbohydrates + 600 mg sodium

Formula B: Solid-Liquid Mix (Ideal for Long Duration)

Per hour:

Formula C: Commercial Product Combination

Choose commercial products with dual-source carbohydrates:

• Maurten 320: 1 sachet = 80 g carbohydrates (ideal for a bottle)
• SiS Beta Fuel: 1 sachet = 80 g carbohydrates
• Tailwind: 1 scoop = 25 g carbohydrates

Bike-Leg Timeline (IM 226 Example, 5 Hours 20 Minutes)

5 hours 20 minutes ÷ 90 g/hr ≈ 480 g total carbohydrates (average 90 g/hr)

Hydration Pairing

90 g/hr must be paired with sufficient water to dilute the concentration:

• Drink concentration 6–9% (6–9 g carbohydrates per 100 ml)
• Additional plain water 200–300 ml/hr
• Total fluid 700–1,000 ml/hr (adjust based on temperature)

Consequences of overly high concentration: Drinks >10% will pull water back into the gut, causing diarrhea and dehydration.

Sodium Pairing

• Heavy sweaters: 600–1,000 mg/hr sodium
• Moderate sweaters: 400–600 mg/hr
• Light sweaters: 300–400 mg/hr

How to pair: sodium in drinks + salt tablets. 0–1 salt tablet per hour (each tablet about 200–400 mg sodium).

Caffeine Strategy

Introduce caffeine in the later part of the bike leg (final 90 minutes):

• Hour 4: caffeinated energy gel (50 mg)
• Hour 5: another sachet (50 mg)
• Before dismounting: 100 mg total, just enough to carry over into the run leg

Common Mistakes

Mistake 1: Using Only Glucose (Single Source)

Result: bloating and nausea once exceeding 60 g/hr.
Fix: Choose products containing maltodextrin + fructose.

Mistake 2: Concentration Too High

Result: gut osmotic imbalance, cramping, diarrhea.
Fix: Pair every 25 g of carbohydrates with at least 250 ml of water.

Mistake 3: Fueling Too Late

Start fueling as soon as you get on the bike; don’t wait until you “feel hungry.” If you’re hungry, it’s already too late.

Mistake 4: Neglecting Practice

90 g/hr isn’t something you can just eat. You must do Gut Training during training (see another article), progressing gradually over 8–12 weeks.

Adjustments for Different Body Sizes

Conclusion

The 90 g/hr dual-source carbohydrate approach on the bike leg is standard equipment in modern triathlon. A 2:1 ratio, 6–9% concentration, paired with sufficient hydration, plus 12 weeks of Gut Training, and you’ll find yourself no longer hitting the wall on the run leg.

Related Reading

• 90 or 120 Grams of Carbs Per Hour on Race Day? Interpreting the Latest Intake Limits
• Decoding Pro Riders’ 120 g/hr Carbohydrate Strategy: The Latest Sports Nutrition Science
• The High-Fueling Era of 90–120 g/hr: Glucose and Fructose Dual Pathways, Gut Training, and Who Really Needs It
• 70.3 Fueling Engineering: The Feeding Assembly Line for the 90 km Bike Leg