HYDRATION GUIDELINES FOR PRE, DURING, AND POST-EXERCISE
4 hours before training / competition drink 400-600mL or the equivalent of about 5-7 mL/kg body weight.
2 hours before training / competition drink 3-5mL/kg body weight.
10-20 minutes before training / competition drink only 200-300mL of water.
The fluid source should be water accompanied by a light meal or snack that provides carbohydrates and electrolytes such as sodium and potassium.
Replace fluids frequently. The key is to drink early and at regular intervals.
150-350 ml every 15-20 minutes.
For low intensity exercise or higher intensity exercise less than 1 hour in duration, water is sufficient.
For high intensity exercise longer than 1 hour, you can choose sports drinks that have 30-60g of carbohydrate / 1L of water.
You should consume 1.5 times the fluid lost during exercise. Weigh yourself before and after activity and replace 450-675ml of fluid for every 0.5kg of body weight lost.
Do not replace this all at once! Drink to comfort level and then divide the rest of the amount required for hydration over time.
Again if the activity was longer than an hour, was of high intensity, or was done in the heat and you were sweating lots, then choose a sport drink to help with electrolyte replacement.