During a trail, the body loses large amounts of water and minerals through sweating. Without adequate intake, runners risk a drop in energy, cramps or even heatstroke. To avoid this, proper hydration is essential. So, what should you drink during a trail?
How to stay hydrated during a race?
If you are embarking on trail preparation, you should know that proper hydration goes beyond just water. You need to compensate for both fluid and electrolyte losses.
Plain water remains the foundation of hydration in trail. It is readily available on course and well tolerated by the body. It is particularly recommended during short efforts or as a complement to a salty diet.
Electrolyte drinks without carbohydrates are very popular on moderate to long trails. They are generally available as tablets or powders to dilute. In addition to water, they contain mineral salts (sodium, potassium, magnesium). They are ideal for rehydrating and compensating mineral losses while keeping sugar intake low.
Isotonic drinks contain water, electrolytes and carbohydrates (around 6 to 8%). They have the advantage of being rapidly absorbed into the bloodstream and provide energy and minerals. They are best suited to long or intense efforts, can be consumed regularly and are well tolerated digestively.
To sum up: on a short trail, plain water is enough. During a moderate effort lasting one to two hours, you can alternate between water and electrolytes. Beyond that — especially during intense effort or in high heat — switch to a full isotonic drink. Test your drinks during training to validate their tolerance in real conditions.
When should you drink during a trail?
Hydration in trail starts before the race even begins. Two to three days beforehand, it is already recommended to drink 1.5 to 2 liters of water daily. Before the start, opt for lightweight mineralised water or pre-race drinks — slightly sweetened with electrolytes — and avoid alcohol or caffeine.
During the trail, you should drink regularly by spreading your hydration rather than drinking large amounts all at once. This technical approach helps avoid hyponatraemia — i.e. over-hydration, which can cause digestive issues. In practice, aim to take one or two sips every 10 to 15 minutes. Do not wait until you feel thirsty to drink, as this risks dehydration. Also make sure to adapt the type of drink to your hydration strategy, and remember to top up at every aid station.
In certain situations, you need to drink more frequently. In warm or humid weather, for example, the body sweats more. Climbs and intense efforts are also moments to anticipate. Finally, racing at altitude leads to faster dehydration — even if you sweat less — because the air is drier.
Hydration during a trail does not end at the finish line. As soon as you arrive, it is important to drink to support recovery. Opt for mineral-rich water, recovery drinks, diluted fruit juices or salted soups.
How much water to drink per hour
The amount of water to drink during a trail depends on several factors. It varies according to the duration of the effort, temperature, humidity, race intensity and your own sweat rate.
On average, it is recommended to drink between 500 and 800 ml per hour. During moderate effort in cool weather, your intake will generally be around 500 ml. In the case of intense effort, high heat or heavy sweating, you can drink up to 800 ml. Some athletes consume up to 1 litre per hour, but this requires solid digestive training.
In trail, the amount of water you need to drink depends more on the type of trail than the number of kilometres covered. You may therefore drink more per hour on a short but intense trail than on a long but moderate one. However, the total amount of water to carry varies. To maintain good hydration on the UTMB, you might set off with 1.5 or 2 liters at the start, as aid stations can be 10 to 15 km apart. Plan a sufficient margin and anticipate how much to carry and consume each hour.
As you can see, drinking properly during a trail matters. By choosing the right drinks and adopting a hydration strategy tailored to your effort, you improve how you feel, reduce health risks and support recovery. Before your race, make sure you test your drinks, quantities and timing during training. That way, you will avoid any nasty surprises on race day.
