The human body is about 60% water. Even the lightest exercise can begin the process of depleting the amount of water in the body. It is very important to stay properly hydrated. When you sweat you lose electrolytes, if you lose too many performance will suffer.
How much should you drink?
The amount of water you should be drinking in a day depends on multiple factors. For example type, intensity and duration of activity, the weather, your age, weight and sweat rate. A common recommendation for hydration is half liter of water per hour of moderate activity, in moderate temperatures. The more intense your activity and higher the temperature the more you need to drink.
Keep water easily available, whether you are walking, hiking, swimming or working out in a gym make sure you have water accessible. Drink more often than not. It is better to take smaller sips of water frequently, rather than chugging a large amount of water infrequently.
Replace your electrolytes. When exercising for an hour or more you increase the chance of losing electrolytes. Drinking a drink that includes electrolytes is a great way of replenishing. A great option to try is coconut water, it is a good source of potassium and magnesium.
Pre-hydrate. By the time you realize you are thirsty you are already dehydrated! Make sure you are drinking plenty of water prior to engaging in activity. The more intense your exercise, the farther in advance you need to begin hydrating.
Rehydrate! It is recommended that for every 1 pound lost while exercising you should drink 16-24 ounces of water after exercise to properly rehydrate.