Snow-covered hills have always been a magnet for Minnesotans of all ages.

Now, a couple of Twin Cities hospitals are sending the message that no matter how you slide down -- on skis, snowboards or sleds -- you should wear a helmet.

Today, Children's Hospitals and Clinics of Minnesota will be handing out free helmets at "sledding safety flash mobs" at Powderhorn Park (1:15 pm) and Lake Nokomis Park (1:45 p.m.) in Minneapolis.

On Saturday, Hennepin County Medical Center (HCMC) is co-hosting the first in a series of "Snow Jams" at Buck Hill in Burnsville to urge skiers and snowboarders to don helmets as part of the hospital's "Save this brain" campaign.

Most people know that skiing and snowboarding can be risky. But why push helmets for sledding?

"The most severe sledding injuries we see are head injuries," said Kristi Moline, the injury prevention manager at Children's. In the past few weeks, she said, four children have been admitted with severe head, neck and spine injuries from sledding. "None of them, to my knowledge, were wearing helmets," she said.

Advocates point to a 2010 study that found more than 20,000 kids and teenagers a year are treated for sledding injuries at emergency rooms -- a third for head injuries.

"It's just a reminder of how delicate your brain is, and you just don't want to mess around with it," said Mary Bensman, a spokeswoman for HCMC's traumatic brain injury center. Since 2008, 91 people have been admitted to HCMC with brain injuries from winter sports, 23 of them from sledding accidents, the hospital says.

Some critics have derided the idea of sledding helmets as another sign of overprotective parenting.

"I've heard those arguments," said Moline, but "we see the injuries on this end." In addition to wearing helmets, she advises sledding feet first and avoiding hills with obstacles. "If one severe head injury is prevented wearing a helmet, it's worth it."