Cold-weather workouts mean wearing lots of thin layers, but knowing just which ones can be tricky. Safe running means protecting yourself from the cold--as well as from your own body heat.

While many runners want to feel toasty immediately, it's better to feel cool early to avoid overheating later. "You should be cold for the first 5 to 10 minutes," says Kara Mitchell, exercise physiologist at the Duke left for Living in Durham, North Carolina. Runners should dress as if it's 15 degrees warmer than the thermometer reads; walkers should wear one layer more than runners.

To cover the core, look for materials that wick-away perspiration -- an increasingly important quality as temperatures drop. "You need to take that moisture off the skin so the body stays dry," Mitchell says.

That goes for underwear, too. "There are a lot more cases of frostbite in the private areas than you want to believe," says Terry Nicola, M.D., marathoner and director of sports medicine and rehabilitation at the University of Illinois in Chicago. "It's painful."

Still, knowing what to wear when can be confusing. Here are guidelines our experts recommend. Of course, in cold weather, wear a fanny pack with emergency ID, and take along a cell phone, gloves, a hat, and a folded-up jacket in case you're hurt or the weather gets rough.

• Temperature range: 50 to 60 degrees

  What to wear: Shorts, long-sleeve shirt and jogging bra. Try SportHill's Explorer Bra with wind-block front, $30. Pull over SportHill's long-sleeved, mock-turtle Explorer Top II with a 12-inch zipper, $92.

• Temperature range: 40 to 50 degrees

  What to wear: Everything above, plus a vest and lightweight gloves.

  A wind jacket with lots of zippers -- including zip-off sleeves so the jacket can serve double-duty as a vest -- is a great investment. We like Perlizumi's versatile Vagabond Jacket, $110.

• Temperature range: 20 to 40 degrees

  What to wear: Replace shorts with long pants or tights; exchange vest for a wind jacket, and add head gear.

  "Remember, 40 percent of your heat is lost through your head," Nicola says. Look for a wick-away hat, face mask, neck gaiter and/or balaclava. Nike's Sphere Pro Laminate Jacket ($120), provides wind- and water-resistance plus moisture management with its new waffle-like, heat-trapping fabric.

  For your legs, try Sugoi's polyester and spandex brushed knit MidZero Tight 40315F, $50.

• Temperature range: 20 to 0 degrees

  What to wear: Add wick-away undergarments. Replace wind jacket with a soft shell, a jacket made of tightly woven, water-resistant material that stretches with you. Add mittens or wool socks over gloves.

  For undies, try Moving Comfort's Micro Bikini with DriLayer, $15.

  If you're thinking about trying one of the new soft shells, we like Columbia Sportwear's Mountain Mobility Sweater, $190.

  SportHill's 3SP Mitt ($30) is made of wind-resistant 3SP -- a combination of super-soft spun polypropylene and lycra -- on the palms, but its fleece on the back is soft for wiping your face or warming your nose.

• Temperature range: Below 0.

  What to wear: Add a face mask, sunglasses, and a second pair of socks.

  Rudy Project's new lightweight Graal SX eyewear ($120 to $135) comes with three sets of different colored lenses – a base color, orange, and clear. Change the lens color to handle various sun and snow conditions.

-- Health Magazine, December 2003

--Julianne Hill