Often underestimated or poorly managed, hydration in trail running plays an almost equally important role as training and nutrition. Proper hydration helps to limit cramps and also to delay muscle fatigue.
But be careful, simply drinking plain water before, during, and after running is not enough to prevent dehydration; the body may need more.
So, what should you put in your water bottle to run efficiently without pain or loss of energy? We explain this clearly and concretely in this article.
Why is hydration essential in trail running?
Trail running is a demanding athletic activity: the body loses significant amounts of fluid through perspiration.
Dehydration greater than 2% of body weight directly impairs your physical and cognitive performance. It can lead to an increased heart rate, reduced concentration, loss of coordination, a feeling of heavy legs, or early fatigue.
During a long-duration race (more than 2 hours), electrolytes (sodium, potassium, magnesium, etc.) are also eliminated through sweat. A deficit of these minerals will lead to an electrolyte imbalance, often responsible for muscle cramps (note that adequate training is the primary reason to avoid cramps).
Your hydration in trail running must therefore allow you to both compensate for fluid loss and restore mineral levels.
Of course, your needs are not the same for a short race as for an ultra-trail. The longer the race distance, the more strategic hydration is essential to maintain balance and prevent muscle problems.
What drink should you choose to prevent cramps in trail running?
Your body needs sodium, potassium, and magnesium to function properly. Without these elements, there is no fluid balance, no nerve transmission, and no effective muscle contractions. An electrolyte deficit therefore increases the risk of cramps and fatigue.
Despite its hydrating properties, pure water is not enough to compensate for mineral losses. This is why drinks containing electrolytes and sugar are preferable.
Composed of a balanced amount of fast-acting sugars and minerals, they are more effective at limiting the onset of cramps and maintaining energy over time.
Here's what you can drink to reduce the risk of cramps:
Mineral waters (like Hépar, Vichy Célestins, or St-Yorre)
● Advantages: natural sodium intake
● Limitations: low in sugar, therefore not ideal during effort but perfect before/after
Homemade drinks (water, lemon, honey or powdered sugar, salt)
● Advantages: economical, natural, easy to make
● Limitations: approximate dosage of minerals; digestive tolerance to be tested
Prepared commercial drinks (tablets / powders)
● Advantages: formulated for targeted carbohydrate and electrolyte intake; convenient to carry
● Limitations: sometimes too sweet or poorly tolerated; may contain additives.
Some studies suggest that sodium bicarbonate, naturally present or added to certain liquids, could help reduce muscle acidity and fatigue. Its direct effectiveness on cramps, however, remains a subject of debate.
Finally, Hydratis tablets represent a simple and reliable solution. Easy to dilute in a water bottle or flask, they provide a good intake of electrolytes and trace elements (zinc, manganese) with a very slight dose of sugars to promote intestinal absorption. A practical and complete alternative, useful before, during, and after races.
How to hydrate properly before a trail run to prevent cramps?
Anticipating fluid and mineral losses is the best strategy to reduce the risk of muscle fatigue and cramps.
Good hydration in trail running therefore starts several days before the race.
Three days before until the day before, drink at least 1.6 to 2 L/day, divided into small quantities throughout the day, even without feeling thirsty. Clear and frequent urine is a good indicator of sufficient intake.
On race day:
● Two to four hours before the start, you can consume between 5 to 7 ml of fluid per kg of body weight. This is approximately 350 ml to 500 ml of water for a 70 kg trail runner.
● One to two hours before, an additional intake of 150 ml to 200 ml can be considered.
During this preparation phase:
● Prioritize beverages rich in sodium or other electrolytes.
● Focus on foods that contain enough potassium (bananas, potatoes, green vegetables, etc.) and magnesium (almonds, legumes, dark chocolate, etc.).
● The consumption of gels, fruit pastes, or energy compotes can also be coupled with an electrolyte drink.
Hydration strategy during a trail run: when and how much to drink?
Drink when thirsty or at regular intervals?
During a trail run, certain signs should alert you: dry throat, pasty mouth, shortness of breath, dizziness, sudden fatigue... However, waiting until you're thirsty is already a sign of dehydration.
For a race longer than two hours, follow a strict hydration plan, to be adapted according to the weather, terrain difficulty, and altitude. The ideal is to drink 150 to 250 ml every 15-20 minutes, even if you don't feel thirsty.
Caution: drinking excessive plain water can dilute the sodium concentration in the blood. This phenomenon, called hyponatremia, can have serious consequences (swelling, confusion, seizures, loss of consciousness, coma...).
To avoid it, it is preferable to drink a sodium-containing drink during the activity.
Transporting your water efficiently: what solution to choose?
The choice of container is essential for proper hydration.
Soft flasks are lightweight, easy to fill, and ideal for short trail runs. Their only limit: a small capacity that requires frequent refilling.
A water bladder or camelback, on the other hand, is more suitable for long distances and ultras without aid stations, as it offers a larger capacity (up to 2 L).
To easily carry your containers during your trail runs, opt for suitable equipment.
For short runs, choose a hydration belt or vest. For longer formats, prefer a hydration pack with front pockets for flasks and a back pocket.
The price of each of these accessories varies depending on the quality of the materials and functionalities. In any case, invest in a reliable system to avoid leaks or discomfort during the event.
Post-trail hydration: how to recover well and reduce the risk of cramps?
At the end of the course, the goal is clear: you must replenish fluid and electrolyte stores to help your body recover.
Within the hour that follows, it is crucial to consume a significant amount of electrolytes. The goal is to replenish water, electrolytes, as well as carbohydrates and proteins.
Natural fruit juices, salted vegetable broths, smoothies, etc., are also alternatives you can definitely use.
To know how much to drink after exercise, weigh yourself before/after without your clothes. The difference found corresponds to the amount of water lost during the trail run. It is recommended to drink 1.5 times this amount.
If you have lost 2 kg, for example, you must then consume 1.5 L x 2, i.e., 3 L of liquid to refuel. Do not drink it all at once; divide the intake over 2 to 4 hours.
Finally, as mentioned earlier, do not forget minerals such as magnesium, potassium, sodium, and calcium. They are also essential for better restoration of muscle function and prevention of post-trail cramps.
Conclusion
In summary, good hydration in trail running is not improvised. It is a strategy to think about beforehand, to adjust during, and to continue afterward. It conditions not only your performance but also your recovery.
Plain water alone is not enough to meet the needs of a body subjected to intense effort. It is essential to compensate for mineral losses by prioritizing drinks adapted to your needs.
Bibliography
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