MONTREAL - The recent commercialization in Canada of jumping stilts has raised concerns among doctors who are worried about head injuries suffered by people who practise "powerbocking."

The shiny, metallic, curved springs are strapped on just below the knee and vendors say they allow users to jump higher, run faster and even perform acrobatic backflips.

Enthusiasts of the stilts are known as "powerbockers" in honour of Alexander Boeck, the German aerospace engineer credited with inventing them in 2003.

More recently, they were brought to world attention when 200 people performed on them at the closing ceremonies of the 2008 Olympics in Beijing.

The stilts, which are made of composite fibreglass, have caught on in Europe and Asia but there are no formal studies on the number or the type of injuries that result from powerbocking.

Dr. Scott Delaney, a sports medicine physician for the Montreal Alouettes and the Montreal Impact soccer team, says he's worried about head and upper body injuries.

"They are upwards of 18 inches off the ground, so when they fall they're going to be falling straight on their head if they fall backwards," he said in an interview.

Delaney said there is also the risk of elbow, shoulder and hand injuries, especially if a runner falls forward on the stilts and tries to put an arm out to break a fall.

Delaney would like to see the stilts sold as a package featuring a helmet, wrist guards and elbow and knee pads.

"I just really worry," he added.

But Marlyn Gagne, a Montreal distributor for the Power Strider brand in Canada, says the stilts are no more dangerous than in-line skates.

"And I would say it's safer because it's easier to keep your balance than it is on skates," she insisted.

Gagne said she has sold at least 300 pairs in Quebec since May and has had no reports of any injuries, adding the stilts can also help people shed extra weight.

"I would say that once you get on them, you can burn up to 400 calories in 15 minutes (because) it's very demanding physically."

The stilts come in different sizes and can be used by children.

"There are junior models that retail for around $300," Gagne said. "That's for eight-year-olds or a child between 60 and 70 pounds."

The adult models of Power Striders generally retail from $400 to $600.

It's one of two major brands of the Chinese-made jumping stilts currently on sale in Canada.

Peter Filippelli, who distributes the Fly Jumper brand online, says parents shouldn't worry too much about young powerbockers.

"Kids aren't too likely to get hurt on them," he said in an interview from his business office in Vaughan, north of Toronto.

"They're only small-scale versions of adult models, they're only six inches off the ground and kids can hardly jump two feet high on them."

Filippelli, who has been selling his stilts since March and hopes to put them into retail stores, said there's been a lot of interest in the West, especially in Calgary.

But he would not discuss sales figures for major Canadian centres which include Vancouver and the Greater Toronto Area.

"We gotta say that Calgary has actually been picking up more than Toronto," Filippelli said.

Filippelli is cautioning buyers to beware because a number of knock-offs have shown up on the Internet.

"You can tell by the price," he said. "You'll see somebody selling a pair of Fly Jumpers for $180.

"With grey-market products, it's very easy for the springs to snap and the welds to just give out.

"You have a risk of serious injury due to the fact that the product is not well-designed," he said.

Ian Shrier, a consulting medical director for the Cirque du soleil, says anybody who is just starting to use the stilts must be careful.

He also adds that anything which helps promote physical activity is good, as long as it is used intelligently.

"If people are smart about it , they will hopefully catch on to the safety part and be prudent from the outset, instead of waiting until we get a rash of injuries," Shrier said.