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/race day by drinking up to 600ml of fluid with two hours to go until the match starts. Then with 15 minutes to go drink around 500ml of fluid.
Once the match/race has started, it is important to consume liquid when you can and if possible, aim for 100-150ml every 15 minutes. 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. 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.

Dehydration typically leads to a 2-3% reduction in sporting performance. The link between dehydration and performance is:

• Your blood volume decreases, so less blood returns to your heart.
  • The amount of blood your heart pumps with each beat decreases.
  • Less oxygen-rich blood reaches your working muscles.
  • Your muscles have less oxygen with which to produce energy aerobically.
  • You must move at a slower pace.