SmarterFitter

A simple way to determine how much to drink is to weigh yourself before and after a typical workout. Water loss can be substantial: A 150-pound person can lose more than a pound of fluid during a brisk walk for just half an hour on a hot day. For each pound lost, plan to drink about two additional cups during or after your next session. If you gained weight during the workout, you drank too much. That can disturb your body's sodium balance, potentially causing serious illness. After a few weigh-ins you'll have a good idea of how much you need to stay well hydrated.