The simple fact is that as we exercise our bodies lose fluid through sweat.
We need to replace the lost salt and water that leaves our bodies during exercise. Although everybody is different, you should aim to replace about 50% of the water you lose through exercise, during exercise.
The remaining amount can be consumed during recovery.
There are a number of factors that affect your level of fluid loss during exercise:
Intensity of Exercise
Some people worry about feeling bloated or uncomfortable during exercise from consuming too much water.
This is less of a concern than becoming dehydrated. You should aim to keep a regular intake of fluid during the course of the exercise.
If you want a more tailored hydration plan for exercising, speak to a dietician.