Sister act: The female pro computer-gamers who are pounding the boys into submission

The trouble with being a woman who's really good at computer games is that when you're spoiling for a fight and you go online in search of one, no one wants to take you on. Just ask Ruth Harrison, a slight 21-year-old from Stockton-on-Tees with bright red lipstick, stiletto heels... and an unyielding addiction to the fighting game Dead or Alive 4 on the Xbox 360.

Though gaming has long had a well-earned reputation as a male-dominated hobby, women are starting to get in on the act. Harrison is one of them, part of a small hardcore of female gamers who are good enough to play professionally. Recently, she flew to Los Angeles to take part in the Championship Gaming Series (CGS), trying to earn her team, London Mint, the title of world champions. Ruth isn't just playing for fun, so perhaps it's not surprising she's short of willing opponents. Defeat at Harrison's hands can be brutal and humiliating.

Here, for the uninitiated, is what you can expect when you take her on. You will first choose one of Dead or Alive's panoply of peculiar-looking warriors from an on-screen menu. Harrison will pick her favourite character, Ayane, a 104lb, 16-year-old girl whose stated interests include "beauty treatment" and eating sugared chestnuts. Your digital representations will enter the arena of battle and square up. And then, hardly any time later, and with hardly any idea of how it has happened, you will be routed. Your lumbering avatar will be on its back. And Harrison will be sniggering at you.

There is no such thing as a graceful defeat in the world of serious computer gaming, and Harrison likes to maximise the indignity of those – typically adolescent boys – she beats to a pulp. "I like to talk a lot of trash when I win," she says, referring to her habit of mocking her thwarted rivals over the telephone headset she wears while she plays. "There are a lot of boys who can't stand it when they lose to a girl. Even if you're good." Harrison even had to change the name she uses to play online – it's currently "Strobe" – after her big mouth and taunts made her too many enemies.

Ruth has a younger sister, Sarah, 19, with a similar ability to pound male rivals into the dirt and she too has just turned professional. The girls first got into gaming when they watched their father play Doom, an early-1990s zombie-blasting classic. Seeing their interest, their father bought them a console; nearly a decade later, he's given up, but the two of them are still obsessed. They're aware that it's something of a niche interest.

"Girls at school weren't interested; they were more into clothes and stuff," says Sarah. And both she and Ruth felt it was wise to avoid talking too much about their habit with potential boyfriends. Neither are wallflowers, but they certainly spent more time than most of their peers in front of a screen. "Mum used to tell us we should be going out more," Ruth says, snorting. "I'd just say, 'Where? This is Stockton.'"

As they got too good for the few gamers they did know, the sisters focused on playing each other. Not surprisingly, it also took

sibling rivalry to a new level. Consoles – five of them – have been smashed, and fingers have been slammed in doors. In a bid for a competitive advantage, like a tennis player adjusting the tension of her racket strings, Ruth even customised her control pad – filing down the casing to make the buttons more easily accessible – with a power drill. "We were supposed to use sandpaper," she says flatly, "but it was too slow." The small slice she took off her finger in the process was an acceptable price to pay. Sarah has had little time for such wheezes. She just practised, and practised, and practised.

It's that kind of dedication that earned the sisters their place at the CGS's first big tournament of the year, in Los Angeles. Taking its cue from TV poker, the CGS is arguably the first serious attempt to professionalise gaming. Whatever the results in LA, the sisters stood to make $30,000 each for their few weeks' work; a successful run could mean anything up to $100,000. There is even talk of sponsorship deals, for everything from game controllers to make-up. It's all a long way from Abbey National, where Ruth was working before the sisters earned their places in LA.

To get those places, Ruth and Sarah had to go through an intensive selection process run by the two British teams competing. Even their own mother had her doubts. "She didn't think we'd be good enough," says Ruth. Yet they beat competition from around Europe and bagged the two spots reserved for women, one in each team.

The intensity upped another notch after the trials. For all their expertise, the Harrisons knew the British teams would be at a disadvantage against their American peers: the league is much more widely known in the US, and most of the people they would play against had become accustomed to competing live on stage, rather than in the comfort of their own living-rooms. But that wasn't the biggest source of tension: before they battled anyone else, there would be a much-hyped battle of the siblings – both girls have a gaggle of online supporters – as their respective teams played for the UK's guaranteed spot in the final round.

In LA, however, as the tournament begins, things don't go altogether according to plan. The game options are set up wrong, and Ruth, overwhelmed by the big-match atmosphere, puts her controller down, expecting the bout to be halted. It isn't. Her sister takes full advantage, and London Mint are dealt a blow from which they never recover. The next day, they lose another crucial match to a team from San Francisco. Their tournament is over. "The whole thing was a mess-up," Ruth laments afterwards. "I choked."

And so, a little chastened, Ruth takes a place on the sidelines to watch her younger sister continue the fight for the title. She's not sure if she'll be back next year. "Playing competitively is fun," she reflects, "but I've got some other things I want to do. Dead or Alive isn't going to be around forever. I want to go to uni. I'm thinking maybe business studies." She pauses. "Or maybe something to do with computers."

You go, girl: More barrier-breaking sportswomen

Hanna Ljungberg , the Swedish international footballer, and Birgit Prinz of Germany (pictured), the Women's World Cup's all-time leading goal-scorer, were both invited to sign for the Italian club Perugia's men's team. Both declined; the move was suspected of being a publicity stunt.

Michelle Wie was marked out as a teen golf prodigy by her remarkable driving strength, and she was the youngest person ever to win an event on the US golf tour. But her decision to start competing in men's events in 2003, aged 14, did not go well; she made the cut only once in 13 events, and announced she would not play any men's events in 2008

In 2000, Gayl King became the first woman to compete in the PDC World Darts Championship. The Canadian won the first set against Graeme Stoddart, but eventually lost. "I'd never have been able to show my face again [had I lost]," said a relieved Stoddart – a remark that didn't do much for the game's reputation as a bastion of progressive thinking. King's efforts did, though, get the ball rolling for the inaugural Women's World Championship in 2002.

Lindsey Van, an American ski-jumper who can outjump plenty of her male peers, is at the head of her sport's drive to be included at the next Winter Olympics. There is currently no women's version because, says the organising committee, there aren't enough competitors.

Danica Patrick became the first woman to win an Indy car race, at the Indy Japan 300 this year. Some have complained that the former FHM cover girl has an unfair advantage because of her weight; another pundit dismissed her as a "drama queen". But Formula One team Honda has faith in her talents, and recently signed her up. AB