Hydration is one of the most important factors when taking part in exercise! As you exercise water is lost from the body through sweat and water vapour when you breathe; it is essential that this loss is replaced, as an excessive loss of fluid can impair performance.
Failing to replace the fluid lost through exercise may result in nausea, vomiting or diarrhoea. Heat stroke can also occur because the more dehydrated you are, the less you are able to sweat and therefore less able to control your body temperature.
You can estimate how much fluid you have lost through exercise by weighing yourself before and after. Every 1kg decrease in weight is equivalent to 1 litre of fluid.
Do not drink alcohol or excessive amounts of caffeine. Both of these contribute to increased urine production, making it more difficult for your body to retain fluids during rehydration.