Much of the concern about young athletes and concussions centres around the obvious heavy-hitters: football, hockey, basketball.

But an expert who studies brain injuries in youth sports worries that female-dominated sports like gymnastics and cheerleading are being overlooked.

Carol DeMatteo, an investigator with CanChild Centre for Childhood Disability Research at McMaster University in Hamilton, Ont., says the number of concussions affecting teen girls is on the rise at her clinic.

"We're seeing more and more girls with concussions," she tells CTV News.

"Our clinics now are 50/50. And most of those girls have repeated injuries," she adds.

Brantford, Ont. high school cheerleader Shannon Russell is one of those who've been injured. During practice one day in October, 2009, she got kicked in the back of the head and knocked unconscious. The hit left her with a concussion.

"I had short-term memory loss for a few weeks and major headaches," she says.

Hamilton dancer Carly Stanhope, 18, also sustained a brain injury when she was knocked out by a fellow dancer last December.

"I was at dance class and two of us were doing handstands beside each other and the girl beside me happened to fall out of hers, and kicked me in the head and I hit my head off of the floor," she says.

Stanhope knew right away something wasn't right.

"I was really, really dizzy at first, kind of seeing stars-type of thing, just nauseous, like immediately," she remembers.

Although she rested afterward and took six weeks off dancing, her symptoms lingered. The headaches and dizziness continued and she had trouble learning new dances. The symptoms also began causing problems in her regular life.

"I was really tired all the time, had trouble focusing in school. I noticed changes in my work habits and test-taking skills. Memorizing information was just not possible," she says.

Her marks in biology went from around 90 to the high 60s.

"So that wasn't helping my average at all trying to get into university," she says.

Stanhope continues to be monitored at the McMaster Rehabilitation Clinic, doing balance tests and, memory tests. But eight months later, her symptoms still linger.

Leaders and players in sports like hockey and football are beginning to pay attention to the seriousness of concussions, ensuring that injured players are pulled out of the game and allowed to fully recover before returning to play. But that same level of awareness may not yet be there in female-dominated sports.

DeMatteo says she's seeing a number of female patients returning to her clinic with repeated head injuries, a sign that hits to the head aren't being taken seriously.

"If a child or a teenager goes back too soon, their symptoms last a lot longer. They end up coming back to our clinic for months and months and months," she says.

She adds: "The evidence tells us that 90 per cent of the time, you'll get another injury within a very shot period of time if you're not ready to go back."

That's what happened to cheerleader Russell. She headed to a cheerleading competition less than two weeks after her first injury and got hit in the head again.

She doesn't remember much about the hit but knows she finished the routine. Her team then took her to a hospital. This time, the injury was severe.

Russell had to stop cheerleading for seven months, had to repeat a year of school, and lost her offers for scholarships to U.S. universities.

"That was one of the hardest things: giving up something I had worked so hard for," she says.

Today, she has regrets.

"I wish I had stopped and taken a big break, let my body get back to normal," she says.

Both Russell and Stanhope want to warn other young athletes that the brain is more fragile than they might think, and girls are not exempt from concussions, or the long term consequences.

From a report by CTV's Avis Favaro and producer Elizabeth St. Philip