Pre-Race Carbohydrate Supplementation: A Scientific Approach to Glycogen Loading

In the days leading up to an important race, many cyclists hear the advice: “Eat lots of pasta!” Behind this lies solid sports science, known as “Carbohydrate Loading” or “Glycogen Supercompensation.” Executing this strategy correctly can allow your muscles and liver to store 20–40% more energy than usual, delivering greater endurance in long-distance events.

What is Glycogen?

Glycogen is the form of energy in which glucose is stored as polymers in muscles and the liver:

• Muscle glycogen: Approximately 300–500 grams (depending on training status and body size), providing energy directly to working muscles
• Liver glycogen: Approximately 80–100 grams, maintaining blood glucose stability and fueling the brain and other organs

When glycogen runs out, riders experience the extreme fatigue commonly known as “Bonking,” and performance drops sharply.

Who Needs Carbohydrate Loading?

Traditional Carbohydrate Loading vs. Modern Simplified Method

Traditional Method (Bergström Protocol, 1967)

• 6–7 days before the race: Perform depletion training combined with a very low-carbohydrate diet (3–4 days)
• 3 days before the race: Switch to a high-carbohydrate diet (10–12 g/kg body weight per day)

Disadvantages: The depletion phase leaves athletes fatigued, low in mood, and with reduced immunity, making it difficult to adhere to.

Modern Simplified Method (Sherman Protocol, revised after 1981)

• 7 days before the race: Normal training and diet
• 3 days before the race: Reduce training volume (Tapering) while increasing carbohydrate intake to 8–10 g/kg body weight per day
• 1 day before the race: Light activity (within 30 minutes), maintaining a high-carbohydrate diet

Advantages: No painful depletion phase required, with similar glycogen storage results. This has become the mainstream recommended approach.

Detailed 72-Hour Pre-Race Plan (Example for a 70 kg Rider)

Day 3 Before the Race (D-3)

Target carbohydrate amount: 560–630 g (8 g/kg)

Day 2 Before the Race (D-2)

Target carbohydrate amount: 560–700 g (8–10 g/kg)

• Continue the high-carbohydrate diet
• Reduce high-fiber vegetables (legumes, cruciferous vegetables) to avoid gastrointestinal discomfort
• Reduce fat intake to create more “room” for carbohydrates
• Shorten training to a 30–40 minute easy ride

Day 1 Before the Race (D-1)

Target carbohydrate amount: 600–700 g (8.5–10 g/kg)

• Maintain high carbohydrate intake but choose easily digestible foods
• Completely avoid: high-fat foods, spicy foods, large amounts of raw vegetables, alcohol, and any new foods
• Finish dinner at least 12 hours before the race
• A small carbohydrate snack before bed is acceptable (white toast, banana)

Race Morning

Target carbohydrate amount: 2–4 g/kg (3–4 hours before the race)

• Plain rice porridge or white toast with jam
• 1–2 bananas
• Energy bar (30–60 minutes before the race)
• Avoid: high-fat, high-fiber, and high-protein foods

Common Carbohydrate Loading Mistakes

Mistake 1: The More You Eat, The Better

Each gram of glycogen stored binds approximately 3 grams of water, so excessive carbohydrate loading can make you feel “heavy.” Intake exceeding 10 g/kg body weight provides no additional benefit and may instead cause gastrointestinal discomfort.

Mistake 2: Starting Supplementation Only on Race Morning

Muscle glycogen replenishment requires 36–48 hours. Carbohydrates consumed on race morning primarily serve to top up liver glycogen and maintain blood glucose; they cannot effectively increase muscle glycogen stores.

Mistake 3: Ignoring Training Tapering

Carbohydrate loading must be paired with training reduction to achieve maximum benefit. If you consume large amounts of carbohydrates while maintaining high training volume, the glycogen will be immediately used up, preventing supercompensation.

Mistake 4: Trying New Foods

The pre-race period is not the time to experiment with new foods. Stick to familiar foods to avoid unpredictable gastrointestinal reactions.

Individual Differences Among Athletes

The effectiveness of carbohydrate loading varies from person to person. The following factors influence results:

• Training status: Well-trained athletes have greater glycogen storage capacity, making loading more effective
• Sex differences: Research shows that female athletes may require higher doses of carbohydrate loading to achieve the same effect
• Metabolic type: Fat-adapted riders are less dependent on carbohydrate loading

Conclusion

A scientific carbohydrate loading strategy is one of the most evidence-supported performance enhancement methods for long-distance cycling events. Starting 72 hours before the race, combined with training tapering and choosing easily digestible high-carbohydrate foods, you will arrive at the start line with optimal energy reserves, laying a solid foundation for a personal best.

Related Reading

• Carbohydrate Loading (Carbo Loading): What to Eat Before a Race
• One Week Pre-Race Nutrition Supercompensation Strategy: Maximizing Liver Glycogen Stores
• The Correct Way to Carb-Load for Cycling: A Pre-Race Carbohydrate Supercompensation Guide
• Carb-Loading Three Days Before a Race: Complete Plan and Practical Example