Putting the frighteners on is a new direction for bra ads. Most are aspirational and feel-good; a gorgeous high-breasted model caught in her underwear, smirking or pouting or gazing into the middle distance. "Up to now, bra ads have fallen into just two categories," explains Farah Ramzan, board account director at Abbott Mead Vickers BBDO, the ad agency which devised the campaign. "Women have been portrayed as one-dimensional mannequins or as sexy, vampy seductresses. Our research showed that women were completely alienated by conventional lingerie ads and we wanted to speak a language they could relate to - modern and perky without being patronising."
So, modern, perky, non-patronising and scary? "Are we being over-alarmist? No, we aren't," says Ms Ramzan firmly. "We are cutting through apathy. Women are ignorant about the damange caused to their breasts during exercise. Two out of 10 don't wear a bra at all. There's a lot of interest in wearing the right shoes for training - you wouldn't go to the gym in stilettos. It's just as important to wear the right bra, because exercise can stretch the ligament that supports the breasts, and once it's stretched it will never go back." Yikes, again.
Such tactics are controversial. "It's certain to attract protests for denigrating women when it breaks out of health magazines and onto mainstream poster sites," comments Harriet Green of Campaign magazine, which monitors the advertising industry.
Reaction among a sample of the bra-buying public was mixed. "It's tricky," says Laura, 30, a student. "It's important to wear a good sports bra, but if they're saying, 'Wear this or you'll go droopy and society will render you a non-valid human being', then it's bad. Of course, I don't want them drooping to my knees - they're near enough to my waist already, thank you - but I hate this only-perfection-can-be-beautiful syndrome."
"It's just saying, if you do sport without a good bra, you will get droopy tits, and if you don't want that to happen, buy one of these - just a fact and a solution, surely?" said Sarah, 25, a sales assistant. "I much prefer it to the usual dopey bra ads with some skinny model in her undies."
"Euch. You'd have to run a marathon every day to get breasts like that," said Clare, 28, an office manager. "I think it preys on women's paranoia. It will put people off exercising."
Shock ads, however, are a good way to sell. pounds 400m-worth of bras are sold every year - a rise of more than 50 per cent in the past five years. Finding an original direction for a new ad campaign is a way to gain a bigger slice of this burgeoning market. Push-up bras in particular have been extremely successful: the rivalry between Playtex's Wonderbra and Gossard's Ultrabra has been gleefully covered in the media as the Bra Wars. The Wonderbra's award-winning "Hello boys" ad campaign made a star of Eva Herzigova, now a supermodel - and lifted sales by 41 per cent.
Such aggressive marketing has contributed to a change in bra-buying habits. "Customers are more educated," explains Alison Swan, manager of the lingerie section at London department store Peter Jones. "They buy a wardrobe of bras for different occasions - before, you'd have had one white, one black and a skin-coloured one if you were lucky."
Mrs Swan, a lingerie veteran for 14 years, is in charge of a team of 12 trained fitters, selling about 250 different bras. Ads work, she says. "The media can create interest in ranges. If something is plugged enough, customers will come and look. The Shock Absorber ad is slightly shocking, but very effective. They're getting their message across."
June Kenton of corsetiere Rigby and Peller is similarly keen. "It's a very good advert because it shocks you into realising if you don't wear a good bra you will droop," she says. "It doesn't make fun of women like the Wonderbra and the Ultrabra ads - remember the one where a woman pulls a load of tissue paper out of the other one's cleavage? It makes you worry, but in the right direction - not that you won't be liked if you have small breasts, but that you should do something positive to look after your breasts."
At the moment, says Ms Kenton, stretch lace is in vogue, as is beige that doesn't show under white clothes, and gently padded shapes. But despite the range of styles, colours and variations on offer, it seems that we are hopelessly ineffectual consumers. Seduced by satin, lace, trimmings, denim (yes, really), bows, gingham, alluring displays in department stores, cute little shops on station platforms, mail-order catalogues and the ubiquitous advertisements, most customers completely ignore one vital element: fit.
This, of course, does no harm to the manufacturers. "The bra industry is swollen by women buying the wrong thing," says Ms Kenton. "We reckon 85 per cent of women are wearing the wrong size. Every woman has a drawerful of bras they don't wear, that they've handed out a lot of money for, and they feel it's their fault."
Insisting on a proper fitting is the key. "Ads are all very well, but any woman who buys without trying on is asking for trouble. Stores aren't helping," she adds indignantly. "You get an assistant who was on lampshades last week and is on bras this week, who measures over your clothes.... Well!"
Peter Jones's Alison Swan estimates that between 75 and 80 per cent of her customers turn up in unsuitable undergarments. "The problem is that they pick a bra and say 'I want this in a 34B'. All makes are different and fit in a different way. We try to get all our customers into the fitting- room. After all, you wouldn't buy shoes without trying them on."
Bra buying may be more of a science than an art: but there is some fun involved too. Farah Ramzan explains that bra buyers can be divided into three types: functionals (plain white cotton), indulgers (frothy lacy confections) and enjoyers (mixture of both). Each European nation has its own bra-buying character. "In Germany there are more functionals, in Italy there are more indulgers," she says. "But the ads are all much of a muchness, right across the Continent - the unachievably thin model in a pretty-pretty bra. We hope that the Shock Absorber ads present women as more three-dimensional."
Ad makers, however, may be missing out on an untapped market. A survey by underwear firm Jockey found that one in seven men loves trying on women's underwear.