(CNN) -- She's petite, she's middle-aged, she's bookish, and if she gets a chance, she'll knock you on your keister.



Beth Hollis, second from left, is a librarian who's become a MegaBeth, a roller derby dynamo.



By day, she's Beth Hollis, a 53-year-old reference librarian in Akron, Ohio. By night, she's MegaBeth, an ageless dynamo on the roller derby rink.



"All my life, when I tell people I'm a librarian, they say, 'You don't look like a librarian,' " Hollis said. "And now that I'm a roller derby girl, they say, 'You don't look like a roller derby girl, either.' So I don't know where I fit in."



Hollis has been fitting in at the Akron-Summit County Library for 27 years.



"She's my hero," said Diane Barton, 48, who has worked with Hollis at the library for 18 years. "I just think it's so cool she's doing something so different and so active and so aggressive. You know how we are. We're librarians, so we tend to have that meek and mild stereotype."  Watch her in action as Beth and MegaBeth »



Before discovering roller derby, Hollis had been casting about for a hobby.



"I tried knitting and literally got kicked out of the knitting class for just not being able to get the hang of it," she chortled. "I guess it was just too soon for me to try knitting. I needed something that maybe was a little bit more physical for a hobby."



Boy howdy.



She visited a Rubber City Rollergirls practice last winter after telling her husband, Warren, a retired high school math teacher, that she was going to an audition.



"At that point, I just said, 'I don't care that I have an AARP card in my wallet; I'm going to go for this,' " she said.



Roller derby is a real sport, having ditched the campy, WWE-like spectacle seen on TV in the early 1970s. The Rubber City squad practices six hours a week and competes against teams in Ohio, Michigan, Indiana, Pennsylvania and Kentucky.



A roller derby match, called a bout, consists of two 30-minute halves. Each team has four blockers and one player called a jammer, whose job is to get past the other team's blockers on a 235-foot oval flat track and lap them to score points. Both teams are on offense and defense simultaneously, and the action is fast and rough.



"I think she's awesome," coach Brian "Coachise" Phillips said. "She is 53, so she is our oldest girl on the team, but she works every bit as hard as every other girl on the team, and she is in as good a shape if not better than every other girl on the team."



And she's an inspiration to the other players.



"It makes me actually excited to think that I could play ... for another 30 years, and that's awesome for me, because this is like my favorite thing to do," said Barb "Barbonic Plague" Brown, who at 21 is the youngest player on the team.



Hollis has earned the respect of her team captain, too.



"She's so tiny -- she's probably like 5 feet 4 and maybe 110 pounds or so -- but when she's out there, she's MegaBeth," said Tracy "Eighty-SixHer" Soulsby, 40. "I wouldn't say she's a very hard hitter, but she's a good blocker. Her strength is getting in people's way and then keeping them behind her, not letting them get around her."



The MegaBeth legend grew during a June bout with the Glass City Roller Girls, a team from Toledo, Ohio. Hollis found herself contending with a 6-foot-1, 220-pound foe who goes by the name Pamazon.



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