Nutritional expert Matt Lovell gives you a guide to what you should be drinking before and after a sport's match to help avoid dehydration.
Becks needs plenty of fluids in the summer heat in Madrid
Dehydration is common in many sports, especially in high temperatures and at high altitudes.
The body loses water and important blood salts like potassium.
Vital organs such as the kidneys, brain, and heart can't function as they require a certain minimum of water and salt.
DOES THE BODY HELP PREVENT DEHYDRATION?
The body tries to stay around a temperature of 37 degrees by sweating.
This results in the loss of body fluid. If fluid levels are reduced it can lead to dehydration and heat stroke.
You are probably dehydrated if you are thirsty, have dry lips and a dry mouth.
A more serious form of dehydration occurs if you have blue lips, a weak pulse, quick breathing and confusion.
You should start drinking early on a match day.
With two hours to go until the match starts, drink up to 600ml of fluid.
Then, with 15 minutes to go before kick-off drink around 500ml of fluid.
Once the match has started, it is important to consume liquid when you can. If possible, aim for 100-150ml every 15 minutes.
After the game, try and drink immediately. This will ensure you do not dehydrate.
Every time you play sport, you lose a considerable amount of fluid.
The best way of checking that you are drinking enough is to look at the colour of your urine.
Check urine colour
Clear urine good, dark bad - see doctor
Check weight over seven day period
Stable weight good, losing weight fast bad - see doctor
Check weight before and after game
Small or no weight loss good, major loss bad
Advice: Drink more water if you fail any of these checks
If you are well-hydrated and drinking the correct amount of water it should be a very pale yellow colour.
If your urine is very dark - usually a brownish-green colour - you are dehydrated and have not consumed enough fluid.
A more accurate way of monitoring that you are drinking adequate amounts of fluid is by weighing yourself before and after you play.
For every kilogram lost you have lost a litre of fluid and need to drink 1.5 litres to prevent dehydration.
WHAT SHOULD I DRINK?
Isotonic drinks are the best.
Isotonic drinks contain between 6-8 grams of carbohydrates in every 100ml. They also contain salt which allows the body to use the fluid efficiently.
Indian cricketer Rahul Dravid tops up on the isotonic drinks
Almost all types of non-alcoholic drinks prevent dehydration.
Water is the most popular form of fluid because it is cheap and accessible. It also is very effective.
Some drinks such as cola, lemonade and high energy drinks often contain over 10 or more grams per 100ml.
These kind of drinks stop the body being able to use the fluid because they take so long to absorb.
Tea and coffee are OK in small amounts.
However, avoid excess consumption as they contain a lot of caffeine.
The best drinks when you are not playing sport are water, fruit juices and squashes.