During a trail, the body loses significant amounts of water and minerals through sweat. Without adequate intake, runners risk a drop in energy, cramps or even heat stroke. To prevent 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 water alone. You need to replenish 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 best prioritised for short efforts or alongside salty foods.
Electrolyte drinks without carbohydrates are very popular on moderate to long trails. They are generally available in tablet or powder form to be diluted. In addition to water, they contain mineral salts (sodium, potassium, magnesium). They are ideal for rehydrating and compensating for 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, delivering both energy and minerals. They are best suited to long or intense efforts, can be consumed regularly and are well tolerated digestively.
To summarise: on a short trail, plain water is enough. During a moderate effort of 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 confirm their tolerance in real race conditions.
When should you drink during a trail?
Hydration for trail starts before the race even begins. Two to three days beforehand, it is already recommended to drink 1.5 to 2 litres of water daily. Before the start, opt for lightly mineralised water or pre-race drinks — slightly sweetened with electrolytes — and avoid alcohol and caffeine.
During the trail, you should drink regularly, spreading your hydration rather than taking in large amounts at once. This technique helps prevent hyponatraemia — i.e. over-hydration, which can cause digestive issues. In practice, aim to take one or two sips every 10 to 15 minutes. Never wait until you feel thirsty before drinking, as this risks dehydration. Also make sure to adapt your choice of drink to your hydration strategy, and remember to top up at aid stations.
In certain situations, you need to drink more frequently. In hot or humid weather, the body sweats more heavily. Ascents 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 conditions, your intake will generally be around 500 ml. In intense effort, high heat or if you sweat heavily, you can drink up to 800 ml. Some athletes consume up to 1 litre per hour, but this requires well-trained digestion.
In trail, the amount of water to drink depends more on the type of trail than on the distance covered. You may therefore drink more per hour during a short but intense trail than during a long but moderate one. However, the total amount of water to carry varies. To maintain good hydration during the UTMB, you might set off with 1.5 or 2 litres, for example, since aid stations can be spaced 10 to 15 km apart. Allow a sufficient margin and plan carefully for the amount to carry and consume each hour.
As you will have gathered, drinking properly during a trail is essential. By choosing the right drinks and adopting a hydration strategy tailored to your effort, you improve your performance, reduce health risks and support recovery. Before your race, make sure to test your drinks, quantities and intake timings during training — so there are no nasty surprises on race day.
