You must drink before, during and after you exercise. Dehydration impairs the body’s temperature-regulating mechanism during exercise. The symptoms and consequences of dehydration include a higher heart rate and body core temperature, fatigue and reduced performance.
Make sure you are sufficiently hydrated before commencing your training. Keep an eye on the colour of your urine throughout the day. The more translucent your urine, the better hydrated you are.
Drink before you start to feel thirsty because by the time your thirst mechanism kicks in you will have lost approximately 2% of your body weight in water. If you only go by your thirst cues, you will only drink 50 to 75% of what you actually need. Strive to drink 1.5 to 2 litres a day.
You’re better off drinking small amounts than downing a large amount in one go. Drink at least 0.5 litres of water two hours before you exercise.
During the effort
While exercising, you must drink just as much fluids as you lose because of perspiration. Drink as much as you can without feeling too full. Don’t rely on how thirsty you feel, and strive to drink 125 ml to 250 ml every 15 minutes.
After your effort
You should weigh yourself before and after sports to calculate how much fluids your body loses while you exercise and to know how much you should drink. All the weight you lose can usually be attributed to fluids. So if you lost one kilo, your body lost 1 litre of fluids.
Drink as much as you need to top up your fluids after your effort. Ideally you should drink 125 to 150% of the fluids you lost. Do you weigh one kilo less after sports? Then drink 1.5 litres during the six-hour period after you exercised.