The more active you are, the more water you need to replenish lost fluids; don’t underestimate the amount of fluids you lose from perspiration. In one hour of exercise, your body can lose more than a quart of water, depending on exercise intensity and air temperature. Therefore, you should drink before, during, and after exercising.

For most workouts, water is the best fluid replacements. If you are exercising at a higher intensity, you may need some kind of sports drink after 45 to 90 minutes to replace electrolytes. Sports drinks are not needed for low to moderate intensity lasting less than 60 minutes, unless you are exercising in hot, humid weather.

However, you don’t want to go overboard with water either. If you have too much water and too little sodium, you can enter into a state known as hyponatremia; this can cause brain cells to become swollen with water, leading to confusion, seizures, coma, and even death. This can happen in people participating in long distance events who drink large amounts of water but don’t replenish electrolytes (including sodium). So if you’re participating in an endurance activity, make sure to also consume a sports drink or gel or other energy food that your body can easily digest and that will provide you with the electrolytes you need.