On the wrestling mat at London Shootfighters, one of the UK's top fight clubs, secretary Vicki Jecks, 26, kicks out at her opponent. She wears boxing gloves, but no head protection; he is 6ft tall and wearing knee pads, black stubble and bulging biceps. There are 14 pairs of fighters training here tonight. Dance music thuds out from a boogie box in the corner and tube trains rumble overhead, overlaid by the whack and smack of kicks and punches connecting with rubber shields. Without them, groins, thighs, shins and faces would, by now, be reduced to putty. After this kickboxing session, which lasts up to two hours, Vicki will be doing a mixed martial arts class - training for her first cage fight competition once she has perfected her wrestling technique.
There are now 40 fight clubs in the UK teaching unorthodox "combat sports" with mixed techniques such as submission wrestling, Kumite and Shotokan karate, boxing, Krav Maga - the Israeli self-defence martial art -and Capoeira - an awesome fighting style originally developed by African slaves in Brazil.
Some of the most dedicated fighters are women. Bored of yoga, meditation and beauty therapy, more and more women are training at MMA (mixed martial arts) gyms where they learn to hit and to be hit, to kick, punch, roll, wrestle, break bones and land "killer shots".
Some fights have rules such as no fish-hooking (putting fingers into an opponent's mouth and hooking out the back of the palate), no eye-stabbing, head-butting or groin-wrenching. Others have no rules at all. Typical injuries are broken collarbones, broken limbs, smashed teeth and mashed muscle, but Jecks is not afraid. "One of the girls is injured at the moment, but I have built up a tolerance for getting hit," she says, her brown eyes sparkling, ready for action. She is slim and shorter than most of the men here, but her broad shoulders and steely determination show fighter spirit.
Club owner Paul Ivens, 31, a former bouncer, says women join the club for the same reasons as men: for fitness and self-defence. He half-smiles: "I could kill you with my punch - but I won't. Or I could chop you in the neck." But these techniques are no use against a knife or gun attack: "For that you need a weapon." The atmosphere in here is serious, even primeval. Aggression condenses on the sweating walls. One guy takes off his shirt to reveal an astonishing torso in ultra-sharp fighting condition. He turns and winks at me.
In the "cage" (a wall-netted boxing ring) Sefali Dhani, 31, is sparring with eight male fighters. Later she says, "I'm more confident and more alert since I started nine months ago. I had trouble outside on the street before I came here, trouble from men, and that's partly why I came. Now I feel good about myself and among men." Her diamond nose stud gleams. "It's not a man's sport - that's a stereotypical attitude - it's a woman thing too."
Back on the wrestling mat, Jecks grabs her opponent round the neck with two hands and jabs her knee hard into the shield, which he clutches at groin level. "Relax! Slow!" warns the coach in Polish-cockney, the snake tattoo on his shin shimmering as sweat streaks down. "Don't look down, don't give him time."
Some wear the Shootfighters T-shirt with the club maxim printed on the back in gothic lettering: "Si vis pacem, para bellum" or "if you want peace, prepare for war".
Cool air gusts in as the door opens and a woman walks in wearing red high-heeled shoes, which she takes off to walk across the mat towards the changing rooms at the back of the room. She emerges wearing track pants and a black vest: "I'm here for the submission wrestling," she says in a soft voice. By day Ruth Derbyshire, 21, works as a receptionist in an engineering consultancy.
Ruth started with judo at the age of 15, but found it "soft" and has moved on to MMA. "I was a quiet sweet girl and I couldn't find the aggression at first. I was a shy little chubby teenager when I started and I come from a Christian family." Now her body is toned by anger and attack. "I found that the aggression comes with it. The exercises release aggression and I became more passionate." She fought three years ago in a "Cage Rage" competition in Wembley Arena, but lost to her female opponent. "I'll fight again in 2008. This time I want to win."
After a warm-up of cartwheels, neck rolls, drops and military-style crawls, the wrestling begins with each fighter trying to make the other "tap out" - admit defeat - before they lose consciousness or break a limb. Ivens circulates, giving instruction: "Fight for the clinch ... pummel in ... drop your weight, grip his hips ... knee him!" It's 8.45pm and no one is submitting yet.
Darren Chen, 29, who owns The Fight Factory in Brighton, says, "Some of our classes have 70% women and I've seen a huge increase in women wanting to learn to fight. There's no age limit." His prize female students are Rio Smith, 16, Laura Edwards, 18, and Autumn Neeson, 14. Rio has been fighting for eight years, has a string of titles and trains every day for two hours. "It's a good discipline, good for memory and quick thinking; it helps me at school. I can fight a man of any age."
Laura is learning "safe methods" of fighting. "We learn not to kill but to disarm," she says, adding that she has not had trouble on the street "for a long time now." Autumn trains four times a week after school and is looking forward to "full contact" fighting when she is 16 years old. Chen says he can spot the talent by the dedication shown by girls like Autumn and he wants to give them a chance. Fighting is a leveller: no matter what age, gender, social or ethnic background, there are only winners and losers.
Painter Sarah Maclean, 45, began training one year ago at the Chelsea Shotokan Karate club with her son Alexander, 10. She is a Kumite fighter and faces her first competition in March this year. "I'm scared, but there's no way out," she says. "My fitness levels and body tone are much better than they used to be and the mental focus applies to other things. You learn concentration and determination. It's exciting. You learn to look people in the eye." But it hasn't been easy.
"When a girl first punched me in the mouth during Kumite, it was a huge shock. I'd never been hit in the face before. It was my fault: I should have blocked it. I kicked her back, hard." Maclean is tall and slim, with blue-grey eyes and a quick smile, but her polite manner is not to be underestimated. "Women aren't taught to fight; you don't generally resort to physical violence. But I wouldn't hesitate to hit someone now. If I got attacked in the street I'd try to break their nose, tip them over and punch them unconscious." Her husband, publisher Jamie Maclean, says wryly, "I feel much safer walking the streets now, with my wife at my side".
· Londonshootfighters.com The Fight Factory: 020-8405 4313
