thanks,i didn't know that.

Winterize Your Workout
Allison Van Dusen, 11.09.06, 12:01 AM ET

When summer rolls around, we know exactly how to adjust our fitness routines: Wear clothing that breathes to keep cool, drink more fluids and, if we're smart, pile on the sunscreen.
But we tend to give winter the cold shoulder when it comes to changing the way we work out. And experts say there's a lot more to it than throwing on sweatpants and a jacket. Ignoring the effect cold temperatures have on your body can result in injury, dehydration or just an overall lousy workout.
"People can underestimate the cold," says Gabriel Valencia, a certified strength and conditioning specialist and owner of Focus Integrated Fitness in New York. "They can get dehydrated a lot faster in cold weather without realizing it."

In fact, in the the winter, simply breathing can cause a runner to dry out--when people inhale cold air, their bodies warm and humidify it, causing respiratory fluid loss.
Valencia's recipe for keeping up your fluid levels: Drink two 8-ounce cups of water two hours before a workout, another cup 15 to 30 minutes before and a half to a full cup of water while exercising.
Overdressing also will you put on the fast track to dehydration. "It can be 25 degrees outside but tropical temperatures under your clothes," Valencia says.

Layers, which you can add and subtract depending on the weather, are key. The base layer--the one closest to your body--should consist of an insulating fabric that allows some heat and perspiration to escape, such as Gore-Tex, says Cedric Bryant, the Redmond, Wash.-based chief science officer for the American Council on Exercise. A waterproof outer layer will protect you from the elements.
When figuring out how many layers to wear while exercising, dress as though it's 20 degrees warmer than it is, Valencia says. If it's 40 to 60 degrees outside, one layer will probably do. At 25 to 39 degrees, bundle up. Remember that wind chill can make a massive difference in how cold it feels, and that the areas of the body most vulnerable to frostbite are the hands, toes, ears and nose.

And don't forget a hat. You can lose 30% to 50% of your body heat by not covering your head. The body then has to compensate, expending more energy to keep you functioning the way you should. "You want to burn calories, but not at the expense of peripheral blood circulation," Valencia says.
It may be winter, but sunglasses and sunscreen also should be on your workout wardrobe checklist--particularly if there's snow on the ground.

Once you're properly outfitted, the next step is what Valencia calls a "dynamic warm-up." Instead of sitting down to stretch or diving into toe touches, he recommends movements that mimic the activity you're about to do, such as slow lunges, jumping jacks and arm circles. People are more prone to pulling muscles outside without a proper warm-up.

Before you begin any workout, take safety into consideration, too; it's always a good idea to talk to a doctor before starting fitness routines. People with asthma and heart conditions may want to consider taking their workouts indoors, Bryant says. Cold, dry air can precipitate asthma attacks, and cold stress also can constrict blood vessels, increasing the heart's work demand.

With fewer hours of daylight in winter months, workouts are more likely to be conducted in the dark, making reflective gear another necessity. Bryant, however, recommends trying to get outside while the sun is still shining. If you properly prepare, an outdoor workout can be enjoyable, and light can help prevent seasonal affective disorder, aka the winter blues.
"We tend to get grumpy when we hibernate," Bryant says.
Winterize Your Workout - Forbes.com