Reece, the current face of Nike sportswear, is in the vanguard of a new American fad for "sports models", or "UberBabes". These are professional sportswomen, honed and muscled by "extreme" skiing or world-champion standard quadrathletics, or, like middle-distance runner Suzy Hamilton, by training for the Olympics.
Earlier this year American Vogue breathlessly hailed "the athletic aesthetic". Another magazine, Self, explained in a detailed feature how to "get a gold medal butt" like Olympic fencer Sharon Monplaisir. "Strong Women Are Sexy" explains a recent issue of Fitness magazine (cover star, Gabrielle Reece).
As well as sports star and cover girl, Reece is a sports commentator and has her own television show, and Nike have taken to calling her a "statement-level athlete" - a corporate image-shaper. Ten years ago, her hefty physique would have excluded her from modelling; now this golden UberBabe is paid an alleged $35,000 ( pounds 22,500) per day for fashion shoots. Strength and muscles are no longer dismissed as butch; they are now feminine and sexy.
"It's important to me that people see you can be an athlete and be strong - and also be a girl," explains Reece, though who would dare to disagree with her is hard to imagine.
Melanie Finn, 31, a writer, lives in New Mexico. She mountain-hikes in summer and skis every day in winter. "I'm extremely fit but, compared to the UberBabes, I'm a couch potato," she says. "Of course they are very professional, they do it for a living. But in the kind of outdoor community where I live in the mountains, there are a tremendous number of women who are incredibly fit. When you start to get fit, you feel sexy because you have this really powerful body - it gives you a new appreciation for this fantastic machine that your body is. I think women do it to feel sexy themselves, not to look sexy for men, because some men find it intimidating."
Europe is lagging woefully in the UberBabe stakes. On the fashion model front, the new image is a non-starter. "Look at the last shows in Paris and Milan - there were no muscular, macho girls," says Vincenzo Lieberato of the Elite Premier agency.
"All models are meant to have a fit, healthy body," says Ellis, a scout for Models 1. "Everybody is more body- conscious and health-conscious today and that includes models, but there hasn't been a change towards wanting more muscular girls."
The closest we have to UberBabes in Britain are probably the ludicrous Gladiators. When the Princess of Wales took herself off to the gym, she was roundly condemned - and not for the company she kept there, but because she was "muscle-bound" and "unladylike". She was even compared to Sylvester Stallone.
But while Jodie Kidd-style slenderness is still the catwalk ideal, there has been a change elsewhere. Suddenly several magazines have moved from the obscure specialist-interest/ sports-fanatics sections in the newsagents into the mainstream health and fitness shelves. Ultrafit, Active Lifestyle, Health and Fitness, and Get Active take a very different approach to the business of getting fit to the usual women's magazines "let's get in shape for Christmas/ spring/ summer holidays" regimes. These magazines might have six- page features on aerobic shoe performance, including such details as Propulsive Force ratings, plus lengthy technical analyses of workout routines.
"Women have always done aerobic exercises to music in big groups with an instructor, while the men have drifted off to the weights room," says Charles Mays, publisher of Ultrafit - his magazine's circulation has doubled since the spring.
"Recently women have started joining the men in cross-training, adding weights and circuit training to their routines. Desirable shapes have changed - women want to be, not skinny, but lean and strong. They are looking at the whole fitness scene quite differently. The idea of stepping on the scales and seeing how much you weigh, for example, is old hat to many. If you train for three months, your shape will have changed, but as you gain muscle, your weight may go up slightly."
Playing boys' games is also a factor. "Women are now competing in a whole range of sports that used to be men's domain: rugby, soccer and so on, and to get the fitness they need to play these sports they need all kinds of training - as they do for adventure sports like canoeing and cross- country running," Charles Mays says.
Health and fitness promoters must be praying that this look catches on even more widely. After all, UberBabedom depends on the gym - though in an effort to woo female users, it isn't called the gym any more.
"We're getting away from the sweaty, hard-core body-building gym syndrome," says Andrew Rhys, manager of the swanky new Espree Club just across from the Tower of London. "Now we call it a health club and have a gym, fitness studio, whirlpool bath, beauty treatments, sunbed - we have to offer the whole package, with a nice ambience. Women prefer a friendly, civilised environment."
Of his 2,600-strong membership, around half are women. Serious female bodybuilding is rare, he says - "I know of maybe five. But we encourage ladies to use the free weights area, simply because free weights use far more muscle groups than machines do." So we can all look like Gabby? "The majority of women won't make it," says Mr Rhys dampeningly. "She's been blessed with very good genetics. Great athletes are born, not made."
The Espree reception area looks more like a nightclub than a gym, with its open plan reception, expanses of polished wood, forest-green leather furniture, and glamorous receptionist. But behind the scenes, despite the plush changing-rooms (fresh flowers, fluffy towels) and the cute bar (pre-workout cocktail of apricot, orange juice, peach, pineapple, vanilla and milk - pounds 3), it seems there is no escaping the work-out itself.
So how do real women cope, faced with the likes of SuperGabrielle? Sharon Hill, 32, is scything through a set of situps on the floor. She comes to the gym four or five times a week, and uses weights to keep fit. She is not noticeably downcast or jealous when a picture of Gabrielle springing forth in crop top and knickers is waved under her nose. "She's got a wonderful body - lovely muscles. She looks better than Cindy Crawford, she looks athletic, not like someone like Claudia Schiffer, who looks like she doesn't eat. I'd aspire to look like her, definitely, but I wouldn't make it."
"She's got stunning, stunning legs," says Deidre Bax, 24, of Gabrielle. "I think she looks great ... " She murmurs something vaguely disparaging about the great one's bust. It's true, Gabs is no Pamela Anderson.
"There are a few models everyone would like to look like, but to achieve that look you'd have to have a ridiculous schedule," says Barbara Kollmeyer, 28, who is toiling on the rowing machine. "She looks great - lean but not too skinny - I'd imagine she's working out intensively every day. Sitting in an office counts against you, unfortunately. She looks great, better than a lot of models. I could work out till the cows come home and I'd never have that stomach," she adds.
But could she? If we gave up our day jobs, enrolled at the nearest gym - sorry, health club - and really, really worked, could we all be UberBabes? 'Fraid not, say Frank Eves and his colleague Patricia Clarke, of the Sport and Exercise Sciences Department at Birmingham University.
"We see models and film stars in pretty good shape and often it's nothing to do with exercise - it's their metabolic rate and bone structure," explains Dr Eves, rather brutally. "Exercise has this glamorous image, but you don't become glamorous by exercising. You might feel different, but you won't lose much weight, and without vast amounts of exercise you can't change your fundamental body shape - you can tone up but you can't change shape."
But surely it's better to aspire to being an Amazon than a waif?
"I'm not sure it's any healthier or more realistic, in fact," says Dr Eves. "A truly realistic image that would encourage people to exercise would be sedentary types doing moderate amounts of exercise." Enter the UberBlob.