When you need extra water

As you ramp up your exercise routine this Spring, ensure you're staying hydrated with our advice based on a recent report from the American College of Sports Medicine.

For most moderate exercisers, drinking as much as thirst dictates during or after a workout will usually prevent dehydration. But if you are overweight, over age 65, tend to sweat heavily, or exercise intensely or for a long time, especially in the heat, staying well-hydrated may take extra effort.

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.

As an alternative or additional indicator, monitor your urine. If it's dark yellow or amber after a night's sleep, replenish your fluids by drinking a cup of water, particularly if you'll be exercising that morning. But wait a while before working out, if possible, to let your body absorb the liquid. And drink extra fluid if your urine is dark or scant. If you've sweated heavily for a long time, you'll also need something salty to replenish lost sodium.

For most recreational athletes, the main goal of staying hydrated is to avoid heat stress. So in addition to drinking on hot days, splash water on your face and wipe away sweat, which hinders evaporation. And watch for symptoms of dehydration: feeling sluggish, dizzy, faint, and weak.