Snow wonder

Downhill skiing
Calorie Burn*: 418
Fitness Factor Skiing downhill is not only excellent aerobic exercise, it also builds stamina while strengthening your buttocks, quadriceps, hamstrings, calves and core.
Girl Gone Wild "Doing something I love every day for the sheer joy of it has improved my sense of self-worth. I've also lost weight and become stronger in every way." – Ingrid Backstrom, 26, Squaw Valley, Calif.
Backstrom, a Seattle native, has won the 2003 Subaru U.S. National Freeskiing and the 2003 and 2004 Canadian Freeskiing championships.
She won't ski without ... her Tecnica "Diablo Magnesium" high-performance boots for comfort and stability ($775; tecnicausa.com). And you also won't catch her without her Giro "Nine.9" helmet ($110; giro.com), which offers a snug protective fit, but doesn't mess up her braids.
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Snowboarding
Calorie Burn: 330
Fitness Factor A terrific total-body toner, snowboarding works your core, hamstrings, quads and calves as well as the muscles in your ankles and feet as you twist to steer your board downhill.
Girl Gone Wild "Being out there every day and working hard definitely has a serious impact on your body. I also love that there's always a challenge – new [skills] to learn and new places to ride."
– Anne Molin Kongsgaard, 26, Mammoth Lakes, Calif.
Since 1994, the Oslo, Norway, native has racked up championship honors that include third place in the 2003 Global X Games SuperPipe in Whistler, British Columbia, Canada, and first-place slopestyle at Nippon Open 2000 in Japan.
She won't board without ... her Burton Troop board ($400; burton.com), which she helped the company design for freestyle riding.
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Snowshoeing
Calorie Burn: 557
Fitness Factor Trekking along winter paths in snowshoes, which distribute your weight evenly over the snow so you don't sink through, works the buttocks, hamstrings, quadriceps, calves, core and abs – offering a more intense workout and calorie burn than you'd get on most warm-weather hikes.
Girl Gone Wild "Constantly adjusting to uneven surfaces and using my upper body to help me move through the snow has translated into a more defined waistline. My entire body is challenged." – Helen Cospolich, 27, Breckenridge, Colo.
A member of the U.S. National Snowshoe Team, Cospolich placed third in the 2004 National Snowshoe Championships and won the 2004 Vail Snowshoe Shuffle, North America's largest snowshoe race.
She won't snowshoe without ... her water-resistant Nike Air Teocalli shoes ($100; nike.com); they keep her toes warm and fit snugly into snowshoe bindings.
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Cross-country skiing
Calorie Burn: 557
Fitness Factor One of the best winter cross-training activities for runners and cyclists, cross-country (or Nordic) skiing is easy to learn and an excellent cardiovascular activity. It tones the buttocks, quads, hamstrings, calves, chest, lats, shoulders, biceps, triceps and abs.
Girl Gone Wild "I love feeling in tune with my body and the challenge of listening to it to determine how it is responding to training and external stresses." – Aelin Peterson, 30, Fairbanks, Alaska
In 2000, Peterson gave up a high-paying job as a securities trader in Milwaukee to become a competitive athlete. After a brief stint as a speed skater, she competed in the 2002 Olympic Games on the U.S. Cross-Country Team and has since added 2003 World Championships team member and 2003 North American Sprint Champion to her list of accomplishments.
She won't cross-country ski without ... her Alpina "CSL" boots ($250; alpinasports.com) for great energy transfer from legs to snow. Peterson tracks her workout intensity with a Polar "S610i" heart-rate monitor ($280, polarusa.com).

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*Calorie burn estimates are per hour based on a 145-pound woman.