MINNEAPOLIS - The crowd of sledders at Lake Nokomis Park on Friday looked very different at the end of the afternoon, than at the beginning.

The dozens of young sledders were given free helmets to put on over their ski caps. The helmets were a gift from the Children's Hospital Injury Prevention Program.

"We have seen an increase in severe sledding-related injuries in our hospital over the last couple of weeks," explained Kristi Moline, Injury Prevention Program leader. "A week of planning went into this and we decided to do it."

The youngsters lined up eagerly to be fitted for helmets of the right size from volunteers of the Children's Hospital flash mob, clad in green T-shirts. The occupants of the sleds and toboggans suddenly had hard, plastic shells to cushion the knocks on young noggins.

Parents, like Kirk Frauenheim, of Minneapolis, were delighted with the generosity of the hospital and the city.

"If it keeps kids safe, I think it is a good idea," he said.

The flash mob of about a dozen volunteers arrived by school bus and handed out 100 helmets at Lake Nokomis and Powerhorn Parks.

"These helmets are the result of a helmet sale that we did at Children's Hospitals and Clinics of Minnesota," said Moline. "We did one in the summer. It was a buy one/give one sale. So, we bought helmets and sold them and the helmet sale proceeds went to buy more helmets for our program to do things like this."

Moline understood that generations of sledders enjoyed the winter activity with little more than a knit ski cap. She said things are different now.

"If you look at the injury curve from the 1980s to the 2000s, the injury-related deaths in kids have gone down dramatically because of things like bike helmets which were not available when I was a kid," said Moline.

Minneapolis police, who have used the "Bike Cops for Kids" program to encourage youngsters to wear bike helmets, were on hand to show support for the sledding helmets.

It is estimated at 20,000 children in the U.S. are treated in emergency rooms for sledding-related injuries. Fifteen percent of those are head injuries, many of them are brain trauma.

"Most of the injuries we see when kids are sledding are head injuries, and they are usually the result of colliding with an object or each other," Moline said.

The children on the sledding hill at Lake Nokomis learned that the toboggan goes just as fast with helmets as without. They were all wearing them at the end of the afternoon.