How to plan your marathon water-drinking strategy

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

Be prepared

If you’re taking part in a long-distance running event like the marathon, many months of training and dedication are required to ensure you achieve your goal in an enjoyable way. As the saying goes, “poor preparation predicts poor performance”.

As well as the miles of running you’ll need to put in, 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. Humans 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 your training and performance jigsaw.

Work out what you lose

Each day you lose water through waste in your urine and faeces, skin during sweating and through expired air. When you exercise, your sweating and breathing rate increase. Sweating is particularly important as it helps you keep your core temperature constant and lose the heat generated by your working muscles.

Consider the intensity and duration of your exercise as both will impact on your hydration status. Finally remember that in warmer environments sweating and breathing rates increase too.

Check for dehydration

Research shows that dehydration reduces performance in endurance events – as little as a two per cent loss of body weight has an impact. Some signs of mild to moderate dehydration are a headache, dry mouth, feeling lightheaded or dizzy, and being thirsty.

It’s easy to become dehydrated, so 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 drinking 400-800ml of fluid per hour during a marathon, with the upper level for warmer environments and faster and heavier runners, and the lower level in cooler conditions for slower runners.

Avoid excess

It’s also important not to drink water in excess in a short period of time, as this can lead to a condition called hyponatraemia, which has a number of negative health impacts (although it is not that common in people with healthy kidneys as they simply urinate more).

It can take time to move from a dehydrated to 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 shouldn’t need to do anything special or different.

When training for sessions of up to an hour, it’s also important to drink water after your session and in the time leading up to your next one.

Little and often

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 try not to be obsessed by it if you have started in a hydrated state.

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 the 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 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 where on a loop you can pop home or to the car. You might also consider carrying 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 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 the habit of sipping water as part of your daily routine – at your desk, while watching TV 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 Marathon Day your routine will be quite different – it’s likely 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