Don't run dry - preventing dehydration when running - Brief Article

Running & FitNews, April, 2001

How much water you drink affects not only the quality of your run, but also how far you go. Exercise-induced dehydration reduces endurance, increases body temperature, heart rate, and your perceived exertion, making your regular run seem much harder than usual. Even slight dehydration reduces endurance and performance, and all effects are exaggerated in hot weather. A recent review of the research showed that individuals who drank water before and during exercise, work out longer.

So if you don't want to run out of steam, drink plenty of water--two cups, two hours before exercising, and five to ten ounces every 15 to 20 minutes during your workout. If you run longer than an hour at a time, choose a sport drink to avoid losing too much sodium. If you are an ultra-runner going distances that take you three hours or more, even a sport drink may not have enough sodium. Make sure you add salt to your diet and consider taking along a salty snack like pretzels.

(Canadian Journal of Applied Physiology, 1999, Vol. 24, No. 2, pp. 164-172)