Though it's been around since the 1930s, roller derby has been catching on in recent years, with adult leagues in cities across the country. But it's not just for grown-ups.

Junior roller derby — with kids as young as 6 or 7 — also is growing in popularity. The youngest skaters who compete against one another are known as "Tootsie Rollers."

Scott Viera, coach of the Hoosier Bruisers junior roller derby team in Anderson, Indiana, says the idea is to get the smallest skaters used to the rules and bumping into other skaters. They also learn skills such as how to fall down and avoid injury.

Already for teen skaters, there's a junior roller derby World Cup.

And some hope these young skaters will propel the sport to the Olympics.