How Do Marathon Swimmers Fuel? An In-Depth Guide

Cold water marathon swimming can increase energy expenditure by 30-40% compared to warmer conditions, making the question of how do marathon swimmers fuel their bodies a critical component of success. A strategic and practiced nutrition plan is essential for maintaining performance and preventing energy crashes during long events.

Quick Summary

Marathon swimmers follow a calculated nutrition plan involving pre-race carbohydrate loading and consistent intake of liquid carbohydrates, gels, and electrolytes during the swim.

Key Points

• Carbohydrate Loading: Maximize muscle and liver glycogen stores in the 36-48 hours before a marathon swim by increasing carbohydrate intake.

• Consistent In-Swim Fuel: Aim for a steady intake of 60-90g of carbohydrates per hour during the swim, primarily through easily digestible liquids and gels.

• Strategic Hydration: Replenish fluids and electrolytes, especially sodium, to prevent dehydration and hyponatremia. Consider preloading with a strong electrolyte drink.

• Practice Feeding Techniques: Work with a support crew and test feeding equipment like ropes, sticks, or kayak delivery during training to ensure a fast and efficient routine on race day.

• Avoid Gut Issues: Prevent gastrointestinal distress by practicing your nutrition plan in training and avoiding high-fiber, high-fat, or high-protein foods before and during the race.

• Prioritize Recovery: Immediately after the swim, consume a carbohydrate and protein-rich snack or meal to replenish glycogen and begin muscle repair.

The Science of Fuelling a Marathon Swim

For endurance athletes, particularly marathon swimmers, nutrition is often called the 'fourth discipline' of the sport. These grueling events, lasting many hours, require a carefully managed intake of carbohydrates, fluids, and electrolytes to maintain energy levels and prevent premature fatigue, often referred to as 'hitting the wall'. The body's primary fuel during exercise is carbohydrate, stored as glycogen in the muscles and liver. These stores are limited and typically last only 90 to 120 minutes of high-intensity exercise, necessitating consistent replenishment during the swim. Furthermore, the unique environment of open water, with cold temperatures and the challenge of consuming fuel while swimming, adds layers of complexity that require a specific and well-practiced approach.

Pre-Race Preparation: Stacking the Tank

Proper preparation begins days before the event with a process known as carbohydrate loading. This involves strategically increasing carbohydrate intake to maximize glycogen stores.

• 36-48 Hours Before: Increase carbohydrate intake to 10-12g per kg of body weight daily while slightly reducing fat consumption to manage overall calories and avoid digestive distress.
• Night Before: Eat a high-carbohydrate, low-fiber, and low-fat dinner to top off glycogen stores. Avoid new or heavy foods that might cause stomach upset.
• 3-4 Hours Before: Consume a moderate, carb-rich meal that is easy to digest, such as oatmeal with fruit or toast with honey.
• 1 Hour Before: A small, fast-digesting carb snack like a banana or energy chews provides a final energy boost.
• 90 Minutes Before: Hydrate with an electrolyte drink containing sodium to boost blood plasma volume, helping retain fluid for the swim.

Mid-Swim: The Art of In-Water Feeding

During the swim, consistent and quick feeding is crucial. The goal is to ingest 60-90g of carbohydrates per hour, primarily from easy-to-digest sources, to keep energy levels stable.

• Consistency is Key: Marathon swimmer Sarah Thomas emphasizes consistent intake to avoid major energy fluctuations. Feeds typically happen every 20-45 minutes, allowing for steady energy delivery.
• Liquid Carbs: Many swimmers prefer carbohydrate-rich drinks, often delivered warm, as they are the easiest to consume and digest. These drinks also double as a hydration source, especially important for replacing electrolytes lost through sweat.
• Energy Gels and Chews: Gels provide a concentrated hit of carbohydrates in a convenient, easy-to-carry packet. Some are formulated with caffeine for a late-stage mental and physical boost. Chews offer a solid-food alternative for those who prefer something to chew.
• Solid Foods (Limited): While liquids and gels are primary, some swimmers incorporate solid foods like small pieces of bananas or energy bars during longer swims for variety.

Post-Swim Recovery: Rebuilding Glycogen

Recovery begins as soon as the swimmer exits the water. The first 30-60 minutes post-swim are a critical window for replenishing glycogen and repairing muscles. This is when a combination of carbohydrates and protein is most effective. A 3:1 carb-to-protein ratio is often recommended.

Equipment for In-Water Feeding

Feeding in open water requires specialized equipment to deliver nutrition to the swimmer efficiently and safely. The method used depends on the swimmer's preference and the support crew's setup.

• Rope Feeding: A simple method where bottles attached to a floating rope are tossed to the swimmer from an escort boat. The rope should be long enough to account for drift.
• Feeding Stick: For competitive races or rougher conditions, a long, telescoping pole with a cup holder is used to pass feeds directly to the swimmer.
• Kayaker Support: A support kayaker paddling alongside the swimmer can offer feeds with minimal interruption to the swimmer's rhythm.
• Bottle Choice: Swimmers practice with a specific type of bottle to avoid issues. Wide-mouth bottles are often preferred to minimize air and saltwater ingestion.

Navigating Common Challenges

Marathon swimming is riddled with challenges, and managing nutrition is paramount to overcoming them. For more insights on fueling strategies, U.S. Masters Swimming offers valuable resources on its website.

Stomach Issues

Gastrointestinal (GI) problems affect 30-50% of endurance athletes. The primary cause is reduced blood flow to the digestive system, which is redirected to working muscles. Practice and a careful diet are the best defenses. Avoiding high-fiber, high-fat, or high-protein foods before and during the race is essential. Some swimmers also manage issues by belching to release swallowed air.

Cold Water Considerations

In cold water, the body burns more calories to maintain core temperature. Warm drinks are easier on the stomach and provide a comforting internal heat boost. Maintaining a consistent feed schedule is also part of the thermal strategy, as energy levels help the body generate heat.

Fueling Options: A Comparison

Fuel Type	Key Advantages	Key Disadvantages	Best For
Liquid Carbohydrate Mix	Easy to swallow and digest; provides both hydration and calories; can be warmed for cold swims.	Less calorically dense than gels; requires mixing and a support crew to deliver.	Consistent, frequent fueling throughout the swim.
Energy Gels/Chews	Highly concentrated source of carbs; quick to consume; easy to store (tucked in suit).	Can cause stomach distress if not consumed with water; risk of flavor fatigue; messy.	Quick energy boosts or supplementing liquid intake.
Solid Foods (e.g., Bananas)	Provides fiber and potassium; psychological comfort of real food; slower-release energy.	Difficult and time-consuming to chew and swallow while swimming; can cause GI issues if not accustomed to them.	Longer events where appetite for liquids wanes; requires careful timing.

Conclusion

For marathon swimmers, fueling is far more than just eating; it is a finely tuned science and a practiced art. From meticulous pre-race carb-loading to the consistent delivery of liquid carbohydrates and electrolytes in the water, every detail matters. By understanding the physiological demands, experimenting with different fuel types during training, and preparing for the unique challenges of the open water environment, swimmers can optimize their energy levels and push their limits. Success in ultra-endurance swimming hinges on finding a personalized fueling strategy that is both efficient and well-tolerated, transforming potential weak points into strengths. A well-fueled swimmer is a strong, confident swimmer, ready to tackle the longest distances.

Frequently Asked Questions

How often do marathon swimmers need to feed during a race?

Marathon swimmers typically feed every 20 to 45 minutes to maintain a consistent energy supply and prevent glycogen depletion, though individual needs can vary.

Why is liquid fuel often preferred over solid food during marathon swimming?

Liquid carbohydrates are generally easier and faster to consume and digest while swimming, minimizing the risk of choking and reducing the blood flow demands on the digestive system, which helps prevent stomach issues.

What is the primary cause of stomach problems for endurance swimmers?

The main physiological reason for gut issues is reduced blood flow to the digestive tract during strenuous exercise, which is diverted to the working muscles. Ingestion of too much air or highly concentrated fuel can also contribute.

How do swimmers stay hydrated in cold water when they may not feel thirsty?

Even in cold water, swimmers sweat and lose fluids. They follow a proactive hydration plan, often involving pre-race electrolyte drinks and regular, scheduled sips from a sports drink during the swim, rather than relying on thirst.

What kind of electrolyte drinks are best for marathon swimmers?

Swimmers often use drinks containing a balanced mix of sodium, potassium, and other electrolytes. For longer swims, a standard 4-8% carbohydrate solution is effective. For 'preloading,' some use stronger solutions to increase blood plasma volume.

Should swimmers use caffeine during a marathon swim?

Some marathon swimmers use caffeinated gels or drinks in the later stages of a race to reduce perceived exertion and increase alertness. It should always be tested in training first, as it can affect some swimmers' stomachs.

How is fuel delivered to a swimmer during a race?

Fuel is typically delivered from an escort boat or kayak using a rope with an attached bottle, a long feeding stick with a cup holder, or directly from a kayaker.