Carbohydrate Loading Before a Swim Race: A Three-Day Pre-Race Diet Plan

Introduction

Carbohydrate loading (Carb Loading) is a strategy of systematically increasing carbohydrate intake before a race to supercompensate muscle and liver glycogen stores, providing athletes with ample energy during competition. This strategy is widely known in marathons and triathlons, but it also offers significant benefits for mid-to-long-distance swimming (400 meters and above), marathon-style open water swimming (5 km, 10 km), and multi-day race series.

The Physiological Basis of Carb Loading

Glycogen Storage and Limitations

Under a normal diet, the human body stores approximately 400–500 g of glycogen in muscles and the liver, providing roughly 1600–2000 kcal of energy. For high-intensity continuous exercise lasting over 90 minutes, this energy may run out midway, leading to “hitting the wall”—a sudden drop in pace, muscle weakness, and mental confusion.

The Effects of Carb Loading

Through carb loading, muscle glycogen stores can be increased to 500–900 g, an improvement of up to 50–100%. Research shows that adequate carb loading can:

• Delay the onset of fatigue
• Maintain higher power output or speed in the latter half of endurance events
• Reduce post-race fatigue and recovery time

Which Swimming Events Benefit Most from Carb Loading?

Three-Day Pre-Race Carb Loading Plan

Basic Principles

• Increased carbohydrate proportion: 70–80% of total daily calories (normally 50–60%)
• Reduced training volume: During the tapering period, training volume drops to 40–60% of normal
• Maintained protein intake: Keep at 1.6–2.0 g per kg of body weight to ensure uninterrupted muscle repair
• Moderately reduced fat: Make room for carbohydrates, but not too low (15–20%)
• Reduced fiber: Decrease high-fiber foods 3 days before the race to lower digestive burden and the risk of gastrointestinal bloating

Example: 70 kg Male Athlete (Three-Day Pre-Race Plan)

Three Days Before Race (D-3)

Two Days Before Race (D-2)

One Day Before Race (D-1)

Common Mistakes and Cautions

Don’t Massively Increase Food Portions All at Once

During carb loading, body weight may rise by 1–2 kg due to increased glycogen and water (each gram of glycogen is stored with 2.7 g of water). This is normal and should not cause panic or lead you to deliberately eat less.

Don’t Try New Foods Before the Race

Carb loading should use familiar foods. Introducing new foods before a race may cause gastrointestinal discomfort, which is not worth the risk.

Moderately Reduce High-Fiber Foods

Beans, whole grains, and large amounts of vegetables may cause bloating or digestive issues before a race. Choosing low-fiber options like white rice and white noodles is safer.

Training Volume Must Be Reduced Simultaneously

Carb loading needs to be paired with reduced training volume. If training volume is not cut back, the extra carbohydrates will only replenish what is burned, failing to achieve supercompensation.

Race Morning Breakfast Strategy

After completing carb loading, the goal on race morning is to replenish glycogen lost during the overnight fast:

• 2.5–3 hours before the race: a normal breakfast (white rice, toast, banana)
• 1 hour before the race: a light top-up, such as 300 mL of diluted sports drink
• 30 minutes before the race: 1 energy gel + water

Practical Tips

• Practice carb loading 4–6 weeks in advance: Do a trial run before an important test race or long training session to confirm your gut’s tolerance for a high-carbohydrate diet.
• Track body weight changes: Weigh yourself every morning on an empty stomach during carb loading to confirm that glycogen stores are increasing as expected.
• Prepare backup foods: When racing away from home, pack familiar high-carbohydrate foods in your bag to avoid strategy failure due to unfamiliar food at the race location.
• Mid-race fueling for long-distance swims: For open water events, research aid station locations in advance and prepare energy gels or diluted sports drinks to maintain blood sugar in the latter half of the race.

Conclusion

Carb loading is an important pre-race tool for mid-to-long-distance swimmers, but it requires precise planning and adequate practice beforehand. Systematically increasing carbohydrate intake over three days, combined with reduced training volume, can bring muscle glycogen stores to a peak on race day. Remember: every carb loading session is a learning opportunity. Finding the strategy that best suits your gut and performance is the true competitive advantage.

Related Reading

• Carbohydrate Supplementation Before Running: A Three-Day Pre-Race Carb Loading Strategy
• Swim Pre-Race Nutrition: A Three-Day Carbohydrate Loading Strategy Before Competition
• Carb Loading in Swim Taper Week: Energy Storage Strategies for Distance Swimmers
• Carb-Loading Three Days Before a Race: A Complete Plan and Practical Example