Q: How much fluid should you drink when working out?
A: If you exercise moderately for less than an hour, all you need to do is drink when you’re thirsty—and water is fine. But for prolonged exercise, especially in hot weather, you should make an effort to drink plenty of fluids.
The American College of Sports Medicine recommends drinking fluids (about an ounce for every 10 pounds of body weight) at least four hours beforehand. Also drink at regular intervals during long workouts, even if you are not thirsty, and drink adequately afterwards. For such endurance exercise, beverages with low to moderate sugar content as well as some potassium and sodium, such as sports drinks, are recommended.