Hydration in Endurance Sports: Smarter Strategies, Better Results

Dawn breaks over the mountain pass. The air is damp, the tires roll quietly through the stillness. It’s still cool, but everyone knows: today will be hot. Lisa reaches for her water bottle. The stage is long, she isn’t thirsty yet – but she drinks. Just in case. That’s what she was taught.

Three hours later, she collapses at the roadside. Her circulation fails. The diagnosis comes later: hyponatremia. Too much water, too little salt. The irony: she thought she was doing everything right – and that’s exactly what became her downfall.

Hydration in Endurance Sports: Drinking Until You Drop?

In endurance sports, drinking has become a ritual. Drink a lot, drink regularly – that’s the mantra. But overdoing it can be dangerous. In addition to the well-known danger of dehydration, there’s the silent threat of overhydration.

When we sweat, we don’t just lose water – we lose sodium. If that loss isn’t replaced, blood becomes diluted. The result: headaches, dizziness, nausea, and in extreme cases, life-threatening conditions. Slower athletes who are out longer and drink more frequently are especially at risk.

Everyone Sweats Differently: Hydration is Individual

Water leaves the body through several channels: sweat, urine, and breath. Physical exertion drastically increases demand. But the rate of fluid loss varies by individual. Between 0.5 and 2.5 liters per hour is common – depending on weight, fitness, weather, and genetics.

Women tend to sweat more efficiently. Trained athletes as well. The better your body regulates heat, the sooner sweating begins – a sign of good thermoregulation. General rules like “1 liter per hour” are rarely accurate.

How Much You Really Need – Two Self-Check Hydration Methods

Drinking too much or too little during training can affect performance. To better understand your fluid needs and adjust your hydration individually, two simple methods can help.

1. Monitor Your Urine Color

Urine color is a quick and effective way to assess hydration. Before training, your urine should be light yellow to straw-colored – a good sign.

If it’s darker, drink 200–400 ml of water or a lightly salted drink about 30–60 minutes before your session.

After training, check again. If your urine is significantly darker than before, your fluid intake was likely too low. In that case, rehydrate accordingly and consider drinking more during future sessions.

This method is simple and easy to implement into your daily routine.

2. Sweat Loss Test with a Scale

This method helps you determine how much sweat you lose during training – and how much fluid you should replace.

Step-by-step:

1. Weigh yourself naked before training.
2. Complete a 60-minute workout under realistic conditions.
3. Record exactly how much you drink during that time.
4. Weigh yourself naked again immediately after training.

The difference is your fluid loss. One kilogram of body weight lost equals about one liter of sweat.

If you drank 0.5 liters and lost 1.2 kg, that’s a total loss of 1.7 liters. Divide that by four to get your estimated intake per 15 minutes.

While not a lab value, this test gives a practical sense of your needs – especially under varying conditions like heat, altitude, or longer efforts.

How to Hydrate Properly Before Training

Starting your workout well-hydrated is essential. Drink 5–10 ml of fluid per kilogram of body weight two to four hours beforehand.

For a 70 kg person, that’s 350–700 ml. If your urine is still dark or you don’t feel the urge to urinate, a small sip 30 minutes before can help. Avoid drinking too much at once to prevent bloating or decreased performance.

How to Hydrate During and After Training

During training, it’s important to listen to your body’s signals. Thirst is a reliable indicator – drink when you feel the need. If you notice heavy sweating or are training intensely, especially in hot or humid weather, an electrolyte drink can be beneficial.

Studies show that the need for electrolytes is influenced more by sweat rate and sodium loss than by workout duration alone.

After training, the goal is to gradually restore your fluid balance. Begin by drinking slowly over the next few hours and monitor your urine color (see above: “Monitor Your Urine Color”).

If your urine remains dark, continue hydrating until it returns to a light yellow or straw color. This is a simple and reliable indicator that your body is rehydrated.

Electrolytes should be part of your recovery drinks, especially if you’ve had a high sweat loss or trained in hot conditions.