As runners know, hydration is important in keeping your stamina, especially during the hot summer days. So, if you're planning on taking part in a race, biking, hiking or just taking an afternoon jog, here's important healthful information.

Peter Macdiarmid/Getty Images

According to Health Day News,

" Staying hydrated is critical if you're physically active in hot weather.But individuals have different hydration needs, so you need to assess your personal sweat rate, according to Brendon McDermott at the University of Tennessee at Chattanooga.

"Sweat rate is very simple to calculate: weigh yourself before exercise, with as little clothing as possible; exercise for half an hour and don't drink or use the bathroom for that half hour; weigh yourself again, wearing the same amount of clothing to see how much you've lost," he explained in a university news release.

If you've lost a pound, for example, that translates to about 16 ounces of fluid that you'll need to replace.

When exercising in hot weather, you should be well-hydrated when you begin your exercise and fluids should be readily accessible during your activity. After your activity, it's important to rehydrate as soon as possible within 30 minutes, he advised.-- Robert Preidt

SOURCE: University of Tennessee at Chattanooga, news release, June 26, 2011"