The importance of hydration

Why it is important to drink enough when working out

Staying hydrated is really important, especially if you are training for a semi-marathon or marathon. Below you will find some easy strategies you can follow in order to get enough fluids during your training and marathon.


When you work out your body loses a lot of fluid. You need to replace the body’s water and electrolytes that are lost through sweat. Loosing too much fluid (f.e. 1 kg for a 50kg runner) can negatively affect the performance and increase fatigue. Consuming too many fluids can also have negative impacts, especially if you are running a marathon. This is due to the dilution of blood electrolytes as the water volume is higher in the body.


Hydration strategies

When training, try to estimate how much you sweat. You can do this by weighing yourself before and after a run (after you cool down), and subtracting any consumed fluids. Every 1 kg lost is equal to 1 lt in sweat. So if you run for 2 hours and have lost 1 lt then this means you have a sweat rate of 500ml per hour. This estimation can help you evaluate how much fluids you need to take in to avoid dehydration.


Drink plenty of water (500-600ml) two hours prior the run to stay hydrated. Just before you start, drink a small amount (200ml) and make sure that during your run you match the sweat losses as closely as possible, paying attention not to overhydrate. About 200ml of fluids at every 3,5kg should be a good amount.


What are electrolytes?

Electrolytes play an important role in maintaining the fluid balance in your body. They are found in the sweat, blood and other bodily fluids. Sodium is an important electrolyte that plays a role in hydration; the other electrolytes are potassium and chloride. When you sweat you lose electrolytes and need to replace them to avoid dehydration and muscle cramps. Sodium helps the body retain more fluid, and it is an important mineral to keep you hydrated. For this reason drinking plain water is not as effective as drinking fluids, rich in electrolytes. Sport drinks and gels contain a good amount of electrolytes, and coconut water is another great source of potassium and sodium and great to replenish your body from lost minerals when sweating.


Practice your nutrition and hydration strategy as often as possible during your runs, especially in the last week before your race. Schedule a marathon simulation to make sure everything is working fine, and you are feeling ok.


You can find more details in the following brochures by the Luxembourg Institute of Health, formerly CRP-Santé as well:


Want to get more tips and tricks for training and running in a competition!?

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About the author

Vesela Savova

My name is Vesela Savova and I am a certified diet and nutrition advisor, living in Luxembourg. Nutrition has been a major interest for me for the past 5 years now. It began as my diet evolved and I started paying attention to the foods I ate and their subsequent effects. Eating consciously and focusing on whole foods has transformed my life, and led me to a new career as a diet and nutrition advisor. I have learned how food can really make us feel at our best or our worst. The knowledge I have gained about the importance of nutrition made me passionate about sharing it with everyone I could. This is why I created my blog