How To Approach Your Water Intake During The Marathon

Professor Paul Gately, Professor of Exercise and Obesity at Leeds Metropolitan University, explains how to keep your marathon hydration strategy on track.

If you’re taking part in a long distance running event like the marathon, it’s obvious that many months of training and dedication are required to ensure you achieve your goal and also that you enjoy the experience. As the saying goes, ‘poor preparation predicts poor performance’.

As well as the miles and miles of running you’ll need to put in to get the best out of the experience, it’s also important to focus on foods and fluids during your training and the marathon itself. One of key nutrients you will consume during your preparation, and on the day of the marathon, is water.

Water contains no calories, but it is essential for life. We can survive many weeks without food but only a few days without water. During exercise – and particularly high-intensity exercise such as running – water becomes a critical piece of our training and performance jigsaw.

As part of our daily life, we lose water through waste in our urine and faeces, skin during sweating and through expired air. Obviously, when we are exercising, we increase our sweating and breathing rates. Sweating is particularly important as it enables us to maintain our core temperature at a constant level and lose the heat generated by our working muscles. During exercise we should also consider the intensity and duration as both will impact on our hydration status. Finally it’s important to know that in warmer environments our sweating and breathing rates will increase too.

Scientific research shows that performance in endurance events like running is reduced as people become dehydrated. As little as a two per cent loss of body weight has an impact on physical performance. Some of the signs of mild to moderate dehydration are a headache, dry mouth, feeling light headed or dizziness and feeling thirsty. During a marathon being dehydrated will impact on your physical performance.

It’s easy to become dehydrated so make sure you check your hydration status regularly. One easy way to do this is to look at the colour of your urine: when it is clear, you are well hydrated, when it is dark, you are probably not sufficiently hydrated.

The International Marathon Medical Directors Association has suggested that during a marathon runners drink about 400-800ml of fluid per hour, with the upper level being in warmer environments for faster and heavier runners, and the lower level in cooler conditions for slower runners.

It’s also important not to drink water in excess in a short period of time as this can lead to a condition known as hyponatraemia. This is also something to be conscious of with a number of negative health impacts (although for those with healthy kidneys this is not that common as we simply urinate more).

It can take time to move from a dehydrated state to a hydrated state so rather than thinking about drinking only before a session or on the day of the marathon, think about regular water consumption on a daily basis. This means that when you start your session (or the marathon) you are already properly hydrated, and you should not need to do anything special or different.

When in training, for sessions of up to an hour, drinking water is important but also after your training session and in the time leading up to your next session. On the day of the marathon, make sure you are adequately hydrated at the start, and take on little and often in the few hours before the race. During the marathon be mindful of the need to take on some water but don’t be obsessed by it, if you have started in a hydrated state.

It is clear that drinking water should be considered a key part of your training; by making it a habit you will reduce the risk of dehydration and get the best out of your training and your big day.

Ten top hydration tips:

  • Consuming water is a key part of your training; not being properly hydrated can be as negative as not putting the miles in beforehand.
  • Before you start looking for obscure reasons for difficulties with your training plans, check out that you are adequately hydrated – sometimes we don’t get the basics right.
  • Be adequately hydrated (clear urine is a sign that your hydration status is OK) at the start of any training session and especially on the day of the marathon.
  • During longer training runs make sure you have access to water, this might mean deciding on a loop where you can pop back home or to the car. You might also consider carrying some money with you so you can stop and buy a drink if you start to feel thirsty.
  • Weigh yourself before and after a training run to get an idea of how much water you lose. A two per cent loss will indicate that you have reached a point where performance can be reduced. This will be a good indicator to help you plan your water consumption.
  • Get into a routine of sipping water as part of your daily routine – at your desk, in the office and while travelling are all great times to top up.
  • Sipping water is better than taking large volumes in one go.
  • Make sure you carry a bottle of water with you at all times.
  • Have a water plan for your training and also for the big day.
  • Remember that on the day of the marathon your routine will be quite different, given the time it takes to get to the start, it’s likely that you will wake up and have your breakfast and first fluids earlier. It’s a good idea to try this schedule in a few of your long runs in the weeks before the marathon itself.

Buxton Water is the Official Water of the Virgin Money London Marathon. For more information visit and follow @buxtonwater