Hydration Essentials for Runners: Key Considerations from a Sports Dietitian 

Preparing for a marathon takes months of focused training, strategic planning, and thoughtful fueling. While we often focus on building endurance, increasing mileage, and planning our carbohydrate intake, hydration is an equally vital part of marathon preparation. Proper hydration ensures that you maintain peak performance, reduce injury risk, and recover efficiently. For marathon runners, understanding how to stay hydrated and manage electrolyte levels can make a difference in training, race-day performance and recovery. In this blog, we’ll explore why hydration matters so much for marathoners and provide practical tips to stay well-hydrated before, during, and after the race.

Why Hydration and Electrolytes Matter

Hydration is not only about drinking water. It’s about achieving the right balance of fluids and electrolytes to sustain energy levels, prevent overheating, and avoid conditions like dehydration or hyponatremia (aka low sodium levels in the blood). Hydration and electrolyte replacement are crucial during a marathon for several reasons:

 

1. Maintaining Fluid Balance

During a marathon, you lose a significant amount of water through sweat, particularly if you’re running in warm or humid conditions. Sweat rates vary, but some athletes can lose over a liter of water per hour, which adds up significantly over the course of a marathon. If you don’t replace that fluid, you can become dehydrated, leading to fatigue, cramps, and a decrease in performance. Severe dehydration can even cause dizziness, confusion, and heat exhaustion. 

 

2. Preventing Electrolyte Imbalance

Along with water, sweat also contains electrolytes, especially sodium, potassium, and magnesium. These minerals act as the “conductors” for muscle and nerve function, helping ensure that your body’s electrical signals move smoothly. Sodium, for example, helps manage water balance within cells, while potassium plays a critical role in muscle contractions. Replacing lost electrolytes through sports drinks or electrolyte tablets can help you maintain muscle performance, avoid cramping, and prevent dangerous imbalances.  

 

3. Sustaining Energy Levels

Proper hydration helps deliver oxygen and nutrients to your muscles, which is vital for sustaining energy levels to reach the finish line. A drop in hydration can reduce the efficiency of your cardiovascular system, meaning your heart has to pump faster and harder to circulate blood. As a result, you may feel tired sooner and have a more difficult time keeping up your pace. Staying hydrated allows your muscles to receive oxygen more efficiently, helping you maintain endurance for longer.

 

4. Preventing Overheating

Water also helps regulate body temperature. As you run, especially in warmer conditions, your body produces heat, and sweating is your primary cooling mechanism. If you’re not adequately hydrated, your body’s cooling system becomes less effective, which increases the risk of overheating. Drinking water and consuming electrolytes help your body manage heat efficiently, which is key to avoiding heat-related illnesses, like heat stroke or heat exhaustion.

Pre-Race Hydration: Setting the Foundation

Now that we know why hydration and electrolyte replacement are so important, it’s fair to say that hydration doesn’t just begin on race day; it’s a process that requires attention in your training season and in the days leading up to the marathon. 

 

Practicing hydration during training helps you understand your fluid needs, adapt to drinking on your runs, and fine-tune your electrolyte balance for optimal performance. Building these habits early ensures you’re prepared to manage hydration effectively on race day.

 

Monitoring urine color is a simple way to assess hydration at any time. Pale yellow indicates you’re well-hydrated, while darker yellow suggests that you might need to drink more fluids. Avoid drinking excessive water to the point where you’re running to the bathroom every hour; the goal is to strike a balance and avoid diluting your electrolytes.

Hydration Strategies on Race Day

On race day, start topping up your hydration as early as with your breakfast meal. The goal is to start your race as optimally hydrated as possible (aka aiming for that pale yellow urine color). Once your race has begun, keep the following tips in mind for maintaining proper fluid and electrolyte balance:

 

  1. Start Early: Begin hydrating within the first 15 minutes of your race and consume fluids regularly throughout. Drinking early prevents the need to “catch up” on hydration later, which is harder once dehydration sets in.
  2. Incorporate Electrolytes: Replace electrolytes with sports drinks or electrolyte tablets to prevent imbalances. Drinking plain water alone may dilute the sodium in your blood, which can lead to hyponatremia, especially in long races. Choose sports drinks or electrolyte supplements that contain sodium, potassium, and other essential minerals.
  3. Listen to Your Body: Pay attention to your body’s signals—thirst, dry mouth, or muscle cramps may indicate dehydration or electrolyte loss. Recognize these signs early to avoid more severe issues later in the race. 
  4. Avoid Over-Drinking: While it’s crucial to stay hydrated, over-hydrating can lead to a dangerous condition called exercise-associated hyponatremia (EAH), where sodium levels in the blood become too diluted. Balance is key; take sips as needed but avoid drinking excessive amounts at once.

Post-Race Hydration and Recovery

Rehydrating after the marathon is just as important as staying hydrated during the race. Post-race hydration helps replace the fluids lost through sweat, allowing you to recover more effectively. Drinking water and electrolyte-replenishing beverages soon after finishing can help ease soreness, prevent cramps, and restore normal fluid balance.

 

Within 30 minutes of completing the race, aim to drink fluids containing both water and electrolytes. Consuming a balanced snack or meal with protein and carbohydrates can also help replenish energy stores and support muscle recovery.

Final Thoughts

Hydration plays an essential role in a marathon runner’s success, influencing everything from energy levels to temperature regulation and mental clarity. Maintaining fluid balance, replacing electrolytes, and staying attuned to your body’s signals can help you stay strong and safe as you tackle 26.2 miles. By practicing smart hydration strategies before, during, and after the race, you can avoid the pitfalls of dehydration, sustain your energy levels, and ultimately achieve your marathon goals.


To get support with your hydration plan and figuring out what works best for you, contact us at info@fuelingforrecovery.com or by phone at (202) 738-4726. You can also book an appointment with one of our professionals directly by clicking this link.

References

  1. Stellingwerff, T. Recommendations for the Traveling Athlete: Heat/Humidity & Hydration. https://athletics.ca/wp-content/uploads/2021/07/TR-L2.pdf
  2. Ricardo J.S. Costa, Martin D. Hoffman & Trent Stellingwerff (2019) Considerations for ultra-endurance activities: part 1- nutrition, Research in Sports Medicine, 27:2, 166-181, DOI: 10.1080/15438627.2018.1502188
  3. Martin D. Hoffman, Trent Stellingwerff & Ricardo J.S. Costa (2019) Considerations for ultra-endurance activities: part 2 – hydration, Research in Sports Medicine, 27:2, 182-194, DOI: 10.1080/15438627.2018.1502189

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