GUILDERLAND, N.Y. (AP) _ It's cold. The noon sky is gray and the sledding hill is all ice. Dave Hilderbrandt stands at the crest, watching his 8-year-old daughter and her friend gleefully zoom down on their plastic sled.
Neither cold nor snow can keep the Hilderbrandts from getting regular exercise.
``We've been out here in blizzards,'' said Hilderbrandt, a resident of this Albany suburb. ``Of course, we don't stay long.''
Keeping kids active when the weather is warm is child's play. But parents can have a hard time keeping them moving when ice crystals are forming on the windows. Even though winter weather can be a powerful inducement for kids to play Nintendo, watch TV and just generally hibernate, pediatricians say it is important to make the effort.
Researchers believe children burn about half as many calories in the winter as they do in the summer. Fitness expert Peter Rehor of Camosun College in British Columbia, Canada, said that while children tend to eat more in the winter, the larger problem is a decrease in activity.
Dips in wintertime activity are especially worrisome to pediatricians as they treat more overweight patients. Obesity among children and teenagers has more than doubled in the past 30 years.
Doctors say keeping kids active _ the sort of movement that gets a heart rate up _ is crucial year-round. Dr. Maddy Weiser, a pediatrician who runs Youth Movement Fitness Club in Bryn Mawr, Pa., suggests continuous movement for 45 to 60 minutes multiple times a week.
A big problem is that kids, though crackling with energy, often lack the self-discipline to regularly hit the treadmill or the Stairmaster.
One obvious answer is to get them bundled up and out the door. The Guilderland school district even sends a ``Go Out and Play!'' brochure home with its elementary students in the winter, listing local places to ski, skate, snowshoe and sled, like the hill frequented by the Hilderbrandt family.
``There are some tricky months,'' admitted Colleen Mickle, a physical education teacher at Guilderland Elementary School. ``But if it's not OK for snowshoeing and it's not OK for skiing, then it's good for hiking.''
The trick is to make it fun for kids, said Dr. Susan Adams, a St. Louis Children's Hospital pediatrician. She said parents can lead outdoor games such as snowball fights. Adams said time limits on TV, video and computer make it easier to keep kids active. She suggests keeping it under an hour for younger children.
If you think it's too cold outside, Adams and other pediatricians suggest taking kids to swim in an indoor pool, play indoor team sports such as volleyball or take up individual pursuits like karate. It doesn't have to cost money. Adams said that many cities have free recreation centers and that even a trip to the mall can be an opportunity to squeeze in some exercise.
``You take them up and down the stairs. You don't take elevators or the escalators,'' she said. ``You power-walk them instead of just meandering along.''
Fitness experts stress that it is important for parents to stay positive about exercise and be a good role model _ don't tell your kids to go out in the cold if you're camped out on the couch, experts say. Go out with them.
``It's got to be something that gets the heart rate up,'' Adams said, ``gets them sweating, gets them panting.''