A Moment of Science

What Drinking And Exercise Have In Common

Dehydration is big problem in some sports because you don't feel like you're losing water.

glass of water on a wooden table

Photo: mloge (flickr)

Drinking enough water helps prevent dehydration.

After a day of skiing, bicycling, or swimming, some people find they get headaches — something like a hangover from drinking too much the night before.

Even though exercise is healthy and excessive drinking is not, the headache in either case is your body’s response to the same problem — dehydration.

Dehydration And Sweating

First, another small mystery. If you commute by bicycle, you may find that you don’t seem to sweat very much until after you arrive. Since sweat is your body’s cooling system, you may not sweat very much until your body has begun to heat up.

When you get to work, your body is still trying to cool down and so you keep on sweating.

Swimmers Sweat Too!

But even then, you aren’t really sweating any more than you were toward the end of the ride. It only feels that way because the wind that evaporated the sweat when you were riding is now gone. Swimmers sweat too, but, because they’re in the water, it doesn’t feel like it.

And since high altitude increases the rate of evaporation, downhill skiers also may sweat far more than they realize.

Losing Water

Dehydration is big problem in all these sports because you don’t feel like you’re losing water.

If you run or lift weights, the sweat acts as a psychological reminder to drink, but as you climb out of a swimming pool, your first thought may not be of a glass of water.

Alcohol doesn’t make you sweat, but it does dramatically increase the amount of urine the body produces and so, like exercise, drinking can cause dehydration. That dehydration, either from drinking or from sweating, is what causes the headache.

Keep Drinking Water!

Exercising and drinking–one may be healthy; the other may be harmful. But if you don’t get enough water, either one can be a headache.

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