Hydration for Running and Trail Running: Tips and Recommendations

Hydration for Running

Proper hydration is crucial for recovering from your training, performing well, making progress, and maintaining good health while running and trail running. This article provides recommendations and practical advice on hydration for various distances, including 10 km, half marathons, marathons, and trail running.

How Much Water Should I Drink Daily?

On average, the recommended daily water intake is:

  • Men: Between 1.75 and 2 liters of water per day.
  • Women: Between 1.4 and 1.6 liters of water per day.

These recommendations are based on moderate ambient temperature conditions and moderate levels of physical activity. It’s important to adjust these amounts based on individual needs and factors such as temperature and activity levels.

Additionally, you need to consider the water lost during your runs or trail runs. During exercise, you lose water through perspiration and breathing, so it’s essential to drink enough water before, during, and after your workouts to replenish these losses.

One way to assess your hydration status is by observing the color and quantity of your urine. Dark-colored and small quantities of urine can indicate dehydration, while larger quantities of light-colored urine may indicate good hydration.

How Much Water Should I Drink After Running or Training?

After your workout, it’s important to replenish the fluids lost through perspiration. On average, a runner loses between 0.5 and 1.5 liters of sweat per hour of exercise, with some individuals losing more than 2 liters per hour. These figures vary based on factors such as temperature, intensity of effort, and individual differences.

As a general guideline, it’s advisable to drink regularly in the hours following your workout according to your thirst. A good rule of thumb is to consume a glass of water every 20 to 30 minutes. However, relying solely on thirst can sometimes lead to hydration errors. To determine more precisely how much water you need to drink after exercise, you can measure your fluid losses.

Here’s how you can estimate your fluid losses:

  1. Weigh yourself before your run, without clothing.
  2. Go for a 1-hour endurance run without eating or drinking.
  3. After the run, undress, wipe off your sweat, and weigh yourself again.
  4. Calculate the difference between your weight before and after the run.

The difference in weight corresponds roughly to the amount of water lost during your run. For example, if you lost 1 kg while running, you lost approximately 1 liter of water. It is recommended to drink 1.5 times the amount of fluid lost. So, for every kilogram of body weight you lose, you should drink 1.5 liters of fluid.

Aim to drink around 500 ml within the first 30 minutes after your run, and then continue drinking regularly every 20 minutes until you reach your hydration goal.

Note: You can perform this test in different temperature conditions, especially on hot days, as the amount of sweat lost varies primarily based on temperature and intensity of effort.

How to Hydrate Before a Race or Training Session?

Proper hydration before a race or training session is crucial. In the hours leading up to the event, it’s important to ensure you’re adequately hydrated.

Here’s a hydration plan to follow before a race:

  • Consume 5 to 7 ml of liquid per kilogram of body weight during the 2 to 4 hours preceding the race. For a 70 kg athlete, this corresponds to 350 to 500 ml.
  • 1 to 2 hours before the race, you can add another 150 to 200 ml based on your thirst. Reduce your intake to allow enough time to eliminate urine before the start.
  • Just before the race, you can drink 300 ml of liquid to stimulate bladder emptying and facilitate proper hydration. You can drink water with a pinch of salt or a drink containing carbohydrates (for long or intense competitions) to improve retention and absorption.

Avoid drinking excessive amounts of water before the race. Over-hydration can lead to hyponatremia, especially if large quantities of still water are ingested.

Hydration During a Race (Marathon, Trail Running)

During a running competition, such as a marathon or trail run, maintaining hydration is essential to avoid dehydration, which can negatively impact performance and increase the risk of heat-related symptoms.

Here are some hydration recommendations during a race:

  • For efforts lasting an hour or less, drink water only when you feel thirsty.
  • For efforts lasting over an hour, drink water or a sports drink containing electrolytes (sodium) and possibly carbohydrates. To personalize these recommendations, you can measure your sweat loss to determine the appropriate amount of fluid to drink. Aim to consume between 90 and 95% of the water lost, without exceeding 1 liter per hour.

Generally, you should aim to drink between 0.6 and 1 liter of water per hour, depending on factors such as temperature, intensity of effort, body weight, and sweat rate.

Consider the following additional recommendations for proper hydration during running:

  • Start the race properly hydrated without over-hydrating.
  • Drink according to your thirst, typically between 100 and 200 ml of water every 15 minutes (400 to 800 ml per hour).
  • Avoid drinking large amounts at once and waiting until you feel dehydrated before drinking.
  • For long or intense efforts, consider consuming a hypotonic or isotonic sports drink containing carbohydrates (4 to 8%) and a moderate amount of salt (300 to 700 mg sodium per liter).
  • When trail running, ensure you have enough water to stay hydrated between refreshment points.
  • Test your hydration plan during training to determine the ideal fluid intake for you.

For runs shorter than an hour, you generally don’t need to drink unless the temperatures are very hot.

To avoid over-hydration or excessive fluid intake, which can lead to hyponatremia (dilution of electrolytes in the blood), the most appropriate strategy is to “drink to thirst” for shorter efforts and follow a more precise hydration plan for longer efforts.

What to Drink During and After Running?

Drinks During Running:

When it comes to hydration during a run, you have two options:

  • For efforts lasting up to one hour, drinking still or mineral water is ideal.
  • For longer efforts lasting over an hour, consider a hypotonic or isotonic sports drink containing carbohydrates (4 to 8%) and sodium. This type of sports drink not only ensures good fluid absorption but also provides energy. However, if you consume carbohydrates through gels and bars, you can rely on water for hydration during longer distances.

Here’s a recipe for a homemade sports drink:

Ingredients for one liter of drink:

  • 50 g sugar
  • ¼ teaspoon salt
  • 60 ml orange juice (for taste)
  • 60 ml lukewarm water
  • 840 ml still water


  1. Dissolve sugar and salt in lukewarm water in a bottle.
  2. Stir well to ensure sugar and salt are fully dissolved.
  3. Add the remaining water and fruit juice.
  4. One liter of this drink provides approximately 800 calories, 50 g carbohydrates, and 450 mg sodium.

Post-Run Drinks:

After running, consider the following options for rehydration:

  • For runs lasting less than an hour, still, mineral, or sparkling water is a good choice.
  • For long and intense training sessions or races, drinks containing carbohydrates and proteins can aid in recovery.
  • Water, diluted fruit juices, and sports drinks are all suitable choices for rehydration after training or racing. Skimmed or semi-skimmed milk is also a well-absorbed beverage that can aid in rehydration. It contains carbohydrates and proteins, which are beneficial for muscle recovery.

Here’s an example of a post-race recovery drink:

Mix sparkling water and grape juice in a 500 ml can, using one-third grape juice and two-thirds sparkling water.

Remember, hydration is a critical aspect of running and trail running. Pay attention to your body’s signals, drink according to your thirst, and establish a personalized hydration plan based on your individual needs and sweat rate.

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