The Science of Carb Loading: What Every Endurance Athlete Needs to Know

If your race lasts longer than 90 minutes, glycogen availability becomes a critical limiter of performance. Carb loading increases your muscle glycogen stores, giving you more usable fuel before the start gun even fires.

The modern protocol is simple: 36 to 48 hours before race start, target 8-12g of carbohydrate per kilogram of body weight while reducing training volume. This creates a high-fuel, low-stress environment that tops off stores efficiently.

"The goal is not to eat as much as possible. The goal is to arrive at the start line fully fueled and comfortable."

— Prep Coaching Team

A practical race-week structure

• 3 days out: reduce intensity, keep normal carbohydrate intake.
• 2 days out: increase to 8-10g/kg carbs and reduce fiber-heavy foods.
• 1 day out: maintain high-carb intake and lock hydration/electrolytes.
• Race morning: 1-4g/kg carbs depending on start time and gut tolerance.

Use foods you have already tested in training. Novel race-week experiments are the fastest route to GI issues. Prep helps by translating your personal product library into a carb-loading plan that matches your event demands.