THE CLASS stared into the full-length mirror, waiting for the 'Eye of the Tiger' tape to rewind. I turned to the girl encased in an unforgiving pink Lycra catsuit, and asked why on earth we were here. 'Aerobics is so boring, and this way I can really hurt someone who comes near me,' she said with a smile, and turned to punch her own chin in the mirror.

Miss Pink Lycra is one of numerous girls in Los Angeles who are venting their aggression, firming their buttocks and training to give any unsuspecting date rapist a good sock in the jaw. Executive boxing is the new fad on the West Coast and in America's biggest cities. Since Linda Hamilton toned up her biceps and touted a Kalashnikov in Terminator II, and Michelle Pfeiffer took up kick-boxing to shape the contours of her Cat Woman suit, some women are giving that old leg warmer, Jane Fonda, the cold shoulder.

Executive boxing is modelled on the real thing. It purports to burn more fat better and faster than a normal workout. Designed by professional fighters and fitness experts, it is supposed to increase self-confidence through punch-bag work, combination and skipping-rope drills, shadow boxing and sparring.

More than 500 people - 300 of them women - are attending the executive boxing course at the Bodies in Motion gym in LA. But at the 7pm showing, only about 30 stressed-out professionals were waiting in the airy, mirrored room. The models, waitresses and wannabee actresses had performed earlier in the day.

Novices stood at the front and big boys at the back. While the latter pummelled punch bags, the rookies, all women, began to spar with themselves in the mirror, bouncing backwards and forwards to heavy rock music, smashing up their reflections to an alternative disco step. 'One, two, jab, jab,' shouted the instructor, a small sinewy woman in satin shorts.

Klaus, the huge boxing instructor who runs the gym, says women find it hard to be violent. 'The barriers to aggression are definitely greater in women than in men. When a woman first comes in, she'll throw a great punch and then say, 'I'm sorry'. But that changes very quickly.'

With Miss Satin Shorts urging the class on, there was little chance of any one flaking. 'Get aggressive,' she yelled. The more they beat themselves up, the happier she became.

After attack came defence. The novices dodged imaginary punches, all choreographed into a final routine: one, two, smash your chin, three four, break your cheek bone, five, six, duck the punch, seven, eight, wind yourself.

The second half of the class was taught by Klaus, a former sparring partner of three world champions. The group galloped around a large punch bag suspended from the ceiling, taking an occasional shot at the leather-padded enemy. One painfully enthusiastic man in black shorts whipped around the bag as fast as he could, urging the class to do the same. Miss Pink Lycra began to flag and flop around her bag. 'Imagine the bag is the person you hate most in the world,' urged Klaus. She let rip a flurry of punches. At the mention of hatred, the women were more aggressive than the men. 'If I imagine that it's my ex-boyfriend, I have a great left hook,' said a blonde with a bright smile and a fat ponytail. It was time to take the punch bags down. Mr Black Shorts barged past others in his desire to unchain them and please teacher. The class stretched and bounced some more. 'You've got to want it, need it,' shouted Klaus as they went into the final press-ups.

Suddenly it was all over, and Klaus and Miss Satin Shorts went round the class to congratulate everyone. 'One, two, three,' they shouted in unison. 'More pain]' And they all punched the air. Oh Lord, I thought, I'd rather go home and write to Claire Rayner.