Planning on running a marathon soon? Perhaps for the first time, with the aim of completing the magical distance of over 42 km? Or are you looking to squeeze out those last few extra per cent to improve your personal record? It goes without saying that good preparation is half the battle. You will undoubtedly have thought about the right footwear and sufficient training, but have you also prepared a well-thought-out competition nutrition plan? In this blog we will discuss one of the most important parts of this: hydration.
Water: an indispensable nutrient during the marathon
Whereas the previous marathon blogs focussed mainly on eating carbohydrates, there is a second nutrient that is indispensable for top performance around the marathon: water! Water is involved in hundreds of processes in our body, but one of the most important of these during exercise is the regulation of body temperature. This rises during a marathon due to the production of heat by the muscles. External factors, such as our clothing and especially the weather conditions, can also play a role in this.
Appearing at the start well-hydrated
By starting the marathon well hydrated and continuing to drink sufficiently along the way, you can prevent a significant drop in performance. To be sure that you appear well hydrated at the start, it is best to monitor the colour of your urine the day before the marathon and on the morning of the race. If it is dark in colour, you are probably still a little dehydrated. In that case, be sure to drink more until the colour of your urine turns light yellow.
How much should you drink during the marathon?
How much you should drink during the marathon depends largely on your individual sweat production and the weather conditions. You can prevent this loss of performance by losing a maximum of 2 to 3 percent of your body weight in sweat at the finish line. Someone weighing 70 kg will therefore be able to lose a maximum of around 1.4 to 2.1 litres during their marathon before serious performance loss occurs.
A calculation example of fluid loss and drinking
If this person were to run a marathon in 3.5 hours and lose 1 litre of sweat per hour (= 3.5 litres), he/she would have to drink at least 1.4 litres of fluid during the marathon to stay within this margin of 3% of body weight. This would amount to about 400 ml per hour. However, perspiration varies considerably from person to person.
Calculate your own perspiration
Try to measure your perspiration in different weather conditions in the following way:
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Weigh yourself shortly before the start of the training, without clothes and preferably after going to the toilet.
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Do your training as usual. During the training, keep a record of exactly how much you eat and drink. Also note the temperature.
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Immediately after the training, dry the sweat from your body, go to the toilet again and weigh yourself again.
Optimising your drinking plan for the marathon
With the results of these measurements, you can make a good estimate of how much sweat you will lose and therefore how much you should drink prior to the marathon. With this information, you can plan exactly how much water/sports drink you will take at the various supply stations, for example.
Summary: the most important hydration tips at a glance
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Drinking enough before and during the marathon is just as important as consuming the right amount of carbohydrates. Dehydration makes it more difficult to regulate body temperature, which leads to a loss of performance.
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Therefore, from the day before the marathon, check the colour of your urine. It should be light yellow. If this is not the case, you know you need to drink more.
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In addition, during your preparation, measure your sweat loss several times in different weather conditions. Based on these results, you can fine-tune your drinking plan for the marathon and thus prevent a significant loss of performance!
