Experience can be a great teacher. Full-time neurosurgeon and part-time skier Steven Haines' experiences have taught him the merits of wearing a helmet.

"I wear one, and we strongly advise wearing them," said Haines, the head of the University of Minnesota's Department of Neurosurgery. "Of course, we also see all the terrible things that can happen with head injuries."

A spate of recent deaths from such injuries has renewed the debate about head gear for physical activities. Actress Natasha Richardson died last week after falling during a ski lesson in Quebec. A snowboarder from West Lakeland Township perished after a fall earlier this month. In late February, Garrison Keillor's brother Phil died after falling on his head while ice skating in Wisconsin.

Experts agree that wearing a helmet while participating in recreational activities is always a good idea, especially for children. But they caution that helmets hardly serve as a panacea -- they provide considerably less protection once a person exceeds 14 miles per hour -- and occasionally can be an complacency-inducing problem.

"Sometimes you can put a helmet on a 13-year-old and he thinks he's invulnerable," said Michael Berry, president of the Colorado-based National Ski Areas Association (NSAA). "The helmet's only part of the issue. Behavior and education about when the helmet can be effective are another part."

While doctors called Richardson's death on a beginners' ski slope an anomaly, it reinforces what they have been learning in recent years about cranial injuries: Anyone suffering any lingering effects should seek medical advice immediately, Haines said.

"It's not just getting your bell rung and getting back to normal. If a person is knocked out or stunned and has a period of not functioning normally, then they should stop doing what they're doing and get evaluated," Haines said. "We've learned a lot about concussions and their consequences ... about the risks of long-lasting damage to the brain."

Helmets provide two types of protection, Haines said: "They're obviously best at preventing penetrating injuries. They also absorb a good bit of force before it gets to the brain, and they spread it to a larger area. It's like having two skulls."

Haines added that a helmet can help "protect you from the carelessness of others." But he said most of the skiers he encounters are not wearing helmets. (NSAA studies indicate that 43 percent of skiers and snowboarders wear helmets.) Recreational racers and youth groups are the most likely skiers to be wearing them.

Several Twin Cities ski-area officials confirmed that most of their skiers do not wear helmets, and there's actually a disincentive for the facilities to mandate their use.

"If you require them, then you have to have them available," said Diana Drake of Buck Hill in Burnsville. "It would be too expensive for us to have them for sale or rent."

While Quebec officials are strongly considering a new law requiring helmets for skiers, there are no such mandates in the United States. There was considerable debate on the topic but no legislation 11 years ago, after Michael Kennedy (son of Robert) and Sonny Bono died of head injuries after skiing into trees within a week of each other.

Statistics actually haven't helped the cause for those seeking helmet laws. The NSAA estimates that helmet use is increasing by about 5 percent a year, but said that there has been no drop in fatalities. There were 2.07 deaths per million participants in 2006.

That's far below the fatality rate of 29.4 per million bicycle riders. Yet Minnesota is one of 29 states that has no laws requiring helmets for cyclists, and the other states mandate them only for children of various ages.

And while 22 states have universal mandatory motorcycle helmet laws, Minnesota requires them only for those with instructional/learner's permits. Three states, including Iowa, have no motorcycle helmet requirements whatsoever.

Bill Ward • 612-673-7643