Danielle Konig is an elite-level youth soccer player in Toronto who had never been injured playing the game she loves – until two years ago, when her under-13 team started using larger, international standard-sized balls.

A few weeks after the change, Konig began complaining of soreness in both knees that required ice treatments after games and practices. Her concerned parents eventually booked an appointment with a physiotherapist, who assured them Danielle was experiencing nothing more than mild tendinitis.

She was one of the lucky ones.

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Researchers have found that girls who play competitive youth soccer suffer more serious knee injuries and have a higher rate of concussions than boys do. A growing number of soccer administrators blame the larger and heavier adult ball, which is typically introduced in youth leagues starting when players are 12.

While that standard ball suits the skill set of international superstars such as Lionel Messi and Canada's Christine Sinclair, concerns about the ball's suitability for younger players is growing. It causes additional knee pressure and leg strain when used by younger girls who are still maturing physically.

It also has an impact on older girls aged 14, 15 and 16, said Alan Gould, executive director of the Toronto Soccer Association. "And you will be amazed at the number of those girls who are playing in either ankle or knee braces," he added.

As a result, the TSA has decided to launch a pilot project to see if a smaller, lighter ball might help. Beginning this spring with the start of the outdoor season, the TSA – with 24 clubs and 24,000 players – will experiment with a "female-friendly" ball in its U-13 girls age group.

It will mark the first time that the Eir (pronounced "air") soccer ball will be used in competition by any league in North America, said Majken Gilmartin, a Danish film producer and life-long soccer enthusiast whose passion for the game led to the new ball's development.

Gilmartin, 48, sells the ball through Eir Soccer, a not-for-profit company she founded in 2008 in Copenhagen. The company is named after the Norse goddess of health.

"You're talking about somebody who used to make films and never thought I'd be making soccer balls as a way of living," Gilmartin said in a recent interview.

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Gilmartin said the ball has made some inroads in Europe, mostly in her native Denmark, Sweden and Germany. The Danish Football Association has approved the Eir ball for girls' and recreational women's soccer.

Gilmartin is hoping the pilot project in Toronto will promote more widespread acceptance of the ball in North America. "We don't want to have a sport where young girls want to leave the game after getting injured," she said. "We want them to play, but we want them to play safe."

"The best-case scenario from our perspective is that this ball does what the manufacturer claims it does – that it makes the game more enjoyable and less of an injury risk to younger female players," Gould added.

The standard, FIFA-approved soccer ball used in the adult game for both men and women has a circumference of roughly 70 centimetres (27.5 inches), about three centimetres more than the 4.5 Eir ball. The standard ball also weighs about 425-450 grams (15-16 ounces), compared to 368 grams (13 ounces) for the Eir.

European research conducted on behalf of Eir Soccer claims that using a smaller and livelier ball has a number of benefits to younger, female soccer players. They include: reducing knee pressure; reducing leg strain by up to 40 per cent; increasing ball speed by 13 per cent; reducing the occurences of concussions.

Independent research indicates that physiological differences between the sexes is another explanation for increased injury risk to younger girls who play soccer. The wider female hip means that the tendons that attach to the knee do so at a different angle than on males, giving rise to increased chances of a knee injury when younger, smaller girls kick a heavier ball.

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Eir Soccer estimates the average youth player suffers one serious injury (enough to force someone out of a game) per season, with the greatest amount of injuries suffered by 12- to 19-year-old players.

Officials from Canada Soccer, the national organization that regulates and helps promote the game, would not comment on this story. The Ontario Soccer Association, however, has given its approval for the trial run using the smaller Eir ball.

When the TSA first learned about Gilmartin's ball, officials contacted her and had a dozen sent over to try out. That test took place in early December with U-13 girls at a Toronto indoor facility. The players were not initially told that they were being used as soccer ball guinea pigs.

"I threw a few into the mix with the regular balls first, didn't tell them about it to see if they'd notice the difference," said Toby Neal, an elite-level coach and league administrator of the 4,000-member Toronto High Park FC. "Some of the players noticed the difference right off. When I told them what it was for, that it was geared toward female players, one was like, 'Well, that's sexist.'"

But for the most part, Neal said, the girls gave the smaller ball a positive rating.

"One girl pointed out that she felt her shots were going farther and with less effort, not having to strike it as hard," Neal said. "Mostly they were surprised with the way they could control the ball, even though it was coming harder and faster."

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The TSA will be closely monitoring the reaction when the outdoor season begins.

"One of the things we've said all along is it has to be a viable soccer ball," Gould said. "And by that I mean, it can have all the purported health benefits, but if it doesn't act like a soccer ball is supposed to act, then it's going to be an uphill battle for it to gain acceptance."

Danielle Konig was involved in the initial trial run.

"I was kind of surprised how much further it went, how much lighter it was," she said. "It was just a different feeling on the ball. But I really liked it."