Your body needs fluid to perform- and to function properly. Even just a small fluid deficiency can limit and affect your physical ability, and an excessive intake won’t benefit performance either. To make sure you’re well hydrated is therefore of great importance, especially when training and losing more fluid and salt from temperature regulation (sweat).

We all know that we need to drink, but do you how much, when and if you should have something special in mind when practicing endurance training? That’s what we’re here to tell you!  

Why do we need to drink more when training?

Water is super important for true proper functioning of all body mechanisms. Water helps transport substances throughout the body and regulates temperature and metabolism. Fluid disperses heat during exercise in the form of sweat and increased body temperature, and the body regulates the temperature mainly through sweating. Since we lose more fluid (and electrolytes), we need to make sure to drink more. How much is dependent on intensity, duration, heat and humidity

How much do we need?

When we aren’t training, our approximate fluid need is around 2-3 liters (about 30 ml/kg body weight), preferably, spread out and regularly intaken during the day.  

During exercise, as much as 1-3 liters (intensity, temperature and humidity have a big impact here) of fluid can be lost in an hour, which means that you are required to drink more to maintain the right fluid balance. Everyone sweats at different rates. In temperatures between 40-90°F (4-32 °C), those who sweat a lot can lose between 1-2 liters of fluid during training, while those who sweat lightly can lose between 0.5–1 liters. If you know that you’re someone who sweats a lot – you need to drink more.

How do I know I’m drinking enough?

To make sure you’re well-hydrated, it’s important for you to understand how much water your body needs to perform optimally. You’ll also need to consider conditions and intensity. If it is hot and/or humid, more fluid will be needed. Check what the weather will be like; if it looks like it will be warm, drink more. Remember, always hydrate regularly with small sips, don’t drink too much at once as it’s harder for the body to take up.

All that being said, you have an excellent built-in liquid meter – thirst! Drinking when you are thirsty is an easy way to get enough fluid (most of the time). A fluid intake, despite the lack of thirst, is more of a concern at high altitudes, in warm climates, and/or during days when one or more intensive training sessions are done.

If you want to know exactly how much fluid you lose, the best guideline is to stand on the scales before and after a workout. The weight you lost is the amount of fluid you disposed of (remember to take into account if you added fluid during the session).

Another easy way to control the fluid balance is to control the color of your urine, it should be light yellow. If it’s not, you could probably benefit of drinking more.

REMEMBER! While it is important to drink enough, don’t overdo it. A large intake, especially if consumed all at once, can lead to discomfort in the gastrointestinal tract. A very large fluid intake can also upset the body’s salt balance – which in the worst cases, can lead to a very dangerous condition called hyponatremia.

What should I fill up the bottle with?

For shorter distances water is enough. For longer sessions (>1½ hour) sports drinks are advised because they also contribute with energy (carbs) and electrolytes. These kinds of products should always be well-tested during training sessions before being used during the race. Read more about what you should drink during training here.

If you have a hard time getting enough energy in your diet

Water is always the no. 1 drink when it comes to general health advice. But if you find it difficult to get enough energy in your diet, it can be helpful to drink something that contributes with energy. Liquid isn’t as saturated as regular food, so a glass of milk or juice together with a meal can be a good way to easily increase the amount of energy in your daily diet. 

Before training sessions, drinks contributing energy (carbs) can be great since they give you fast fuel that is digested more quickly compared with food. 

What now?

If you always make sure you have a water bottle nearby, you ensure that you can supply your body with fluid when it needs it (thirst signals). Make sure to remember the circumstances that affect the fluid requirement (intensity, duration, heat and humidity), and keep on sippin! 

Kajsa holds a bachelor’s degree in Dietetics from Umeå University, Sweden. Having worked as a Clinical Dietitian with a focus on dietary treatments for both individuals and groups, Kajsa now supports the Lifesum team in providing professional and evidence-based interventions to users. Kajsa is a self-confessed training nerd and admits her greatest passions are anything to do with food, science and health.

All posts by Kajsa Ernestam