WATER WORKS
By Dr Sarah Rowell, Running fitness.

Taking sufficient fluid on before, during and after training and racing is something that a great number of runners ignore - or do not take seriously enough. Read on to find out what to drink and when.

Over the last ten years or so, running related scientific literature has been dominated by articles and research about the importance of drinking during exercise. Long gone are the days when only wimps drank during marathons. Even so, here's a timely reminder of best practice rather than quackery.

Firstly, why drink? Well keeping yourself adequately hydrated will not make you a better or faster runner sorry. However, (and here I quote from a recent American College of Sports Medicine review): "Physical activity, athletic performance and recovery from exercise are enhanced by optimal nutrition in the form of selection of food and fluids, timing of intake and supplement choices. Dehydration decreases exercise performance and it also increases the risk of potentially life threatening heat injury. Adequate fluid needs to be consumed before, during and after exercise."

The aim therefore is to ensure that you start each training session/race fully hydrated; you do what you can during the exercise to replace fluids and then once you stop you rehydrate all without going OTT, which can be just as bad.

Before exercise

Keep drinking: Depending on where you look, the experts reckon you should be drinking two to three litres a day minimum and on top of that what you need as a runner. One way to help with this is to keep a large bottle of water to hand to keep sipping from. Obviously you need to work out your pre-run stop drinking time to minimise the risk of being caught short later.

Having said that many runners find that drinking up to 500ml of fluid in the form of a 4-8% carbohydrate solution 10 minutes before you start helps with both maintaining fluid balance (see below about a full stomach) and energy provision.

During exercise

Here the consensus is that for sessions under 60 minutes you probably get limited benefit from drinking during the actual exercise (there is some research which shows drinking carbohydrate drinks during interval sessions can help performance). For longer sessions think drink. While fluid balance is not always possible due to high sweat rates, athletes often drink less than 500 ml per hour when sweat rates of more than one litre per hour are possible. Gastric emptying (the movement of water from the gut into the blood stream) is greatest when the amount of fluid in the stomach is high. It is therefore much better to start with fluid in the stomach and then keep topping up little and often, aiming to drink every 15 to 20 minutes. How much is more difficult as this will depend on the temperature and your individual sweat rate (everyone knows someone who comes back from a run absolutely soaking wet, looking like they have been in the rain, while their running partner just has a slight glow). However, it is possible for fluids containing 4-8% carbohydrate to be emptied from the stomach at rates of over 1 litre per hour. Drinking fluids with more carbohydrate in than this will slow down absorption.

After exercise

You should aim to drink up to 150% of the weight lost during exercise. Including sodium either in or with the drink helps the rehydration process.

What to drink?

Gone are the days when water was the drink of choice. We now know that, irrespective of the added bonus of providing additional energy, appropriate sports drinks have fast absorption rates (ie the water gets to where its needed quicker) compared to water. It is not possible to say X drink is better than Y, what is it possible to do is give the key characteristics to look out for. What you will then find is that many of the top sports drinks on the market meet these requirements.

For optimum emptying (rather than optimum energy) drinks should have 4-8% carbohydrate (or sugar), certainly no more, plus some sodium (40-110mg per 100 ml). If you are making drinks up from a commercially available sports drink powder this would equate to 40-80 grams of power per litre of water.

For comparison soft drinks are usually 10-12%, so to be good sports drinks they could be diluted 50:50 with water.