At the Prada emporium in SoHo, the fall shoes have arrived. There are "pony hair" pumps with a keen toe and a modest heel. There are other shoes that look easy enough to wear while navigating an urban obstacle course. But those are not the shoes drawing all the attention on a late summer afternoon.

Prominently displayed next to the store's sweeping staircase is a pair of patchwork Mary Janes with a rounded toe and a four-inch block heel. They are cobbled out of a cacophonous mix of pink python, metallic gold calfskin and about four other shades and textures of leather. When a woman slips them on, her entire body pitches forward as if balanced on the edge of a precipice.

Another pair of shoes drawing coos of delight is a pump in gold and olive tweed decorated with a tiny purple velvet bow and a sunburst of richly hued crystals. The narrow, three-inch heel looks as though it has been etched out of stainless steel and curves inward like the comma heel by celebrated designer Roger Vivier.

These are the sorts of shoes that tempt a woman into recklessness. Like scoundrel boyfriends, vodka-soaked olives and flourless chocolate cake, the shoes have little redeeming value other than a delicious, fleeting pleasure.

No good can come of indulging in them too often. The shoes are bad for a woman's feet. They can wreak havoc on the knees, the back, the joints. High heels shift a woman's center of gravity making her more likely to stumble. A woman cannot run in high heels, leaving her vulnerable.

Yet they cause her back to shift into a more prominent S curve, pushing the pelvis forward and derriere back and forcing her to walk with a hip sway that society generally agrees is sexy. Irresistibly sexy.

A host of companies have recognized and analyzed the illogical psychology at work when a woman buys a pair of shoes. Is it some curious synaptic misfire in the cerebrum that causes so many women to give form precedence over function? In a famous scene from "Sex and the City," Carrie Bradshaw looks into a shop window at a pair of rose-colored heels and coos, "Helloooo, looover." Most husbands do not receive such an enthusiastic greeting after a week-long absence. In 1991, the siren song of shoes was documented by Tuck & Patti in a tune called "High Heel Blues."

I was walking down the street

I was minding my own business

Then these shoes called out from the window

They said hey girl Patti come here you need to wear us.

Patti succumbed. And the shoes were uncomfortable, as high heels tend to be. But now shoemakers are promising that with the aid of advanced technology they can create a high heel that will titillate a woman's imagination while coddling her feet. These promised shoes will protect her joints from undue stress and they will keep her from feeling as though she might topple over at any moment. Manufacturers are striving to create the perfect union of fashion and function -- a goal as potentially lucrative as promising a woman she will be able to have her cake and her form-fitting pencil skirt, too.

Success requires re-engineering. The essential problem with high heels is impact. The click-click of heels on pavement is the sound of the body taking a beating. Because of the angle of the foot and the spindly heel, each footstep sends a shock wave through the body far more powerful and destructive than if the foot were swaddled in a pair of running shoes with thick rubber soles and a level footbed.

"It's like the karate punch. It doesn't have to hit hard, but it hits you fast," says Ray Fredericksen, who runs Sport Biomechanics, a Michigan consulting company that tests footwear for comfort and safety.

Naturalizer, founded in 1927, essentially introduced the notion that a high heel shoe could be comfortable. From the beginning, the company's mission was to create shoes that are both stylish and wearable. Brands such as Easy Spirit and Aerosole followed. In 2000, for instance, Easy Spirit introduced a line of leather business shoes enhanced with Lycra. Cole Haan has incorporated Nike cushioning techniques in some of its dress footwear -- from boots to mules. Geox, an Italian brand that recently opened its first U.S. store in New York, incorporates a porous but waterproof membrane into its shoes that allows air to circulate around the feet, keeping them cool and dry. Other labels, such as Taryn Rose and Trippen, focus on comfort while emphasizing eclectic, artsy and luxury styling.

For decades, companies have been stuffing their shoes full of proprietary padding and cushioning technology. They have painstakingly created lasts -- the forms around which the body of the shoe is molded -- that are welcoming to as many feet as possible. The styling generally emphasizes a roomy toe box, rather than a pointed and constricting one. The heels, when they rise above an inch, are chunky to provide stability and lessen the effect of all those pounds of force shooting through the body.

The "comfort shoe" market, which includes high-tech heels as well as traditional flats like Mephisto and Ecco, has been growing over the past few years and its customer base has been getting younger, according to Footwear News. In the 1990s, the main audience for these shoes were folks in their fifties. Now women in their thirties have become customers. Women spent more than $1 billion on comfort shoes last year, according to the NPD Group, which tracks retail sales.

The lengths to which companies will go to research, create and test their shoes is both admirable and absurd. The improvements in high heels have been incremental, the technology ever-changing and bragging rights quickly claimed. Two enterprising companies -- one on the East Coast and the other on the West -- are indicative of the newest high-heel cobblers currently thumping their chests.

Oh! shoes, based in Portland, Ore., is trying to solve the high-heel conundrum by slowing the speed at which force is absorbed by the body. By dissipating the impact, the body is protected from the equivalent of a sucker punch.

Insolia, in New Hampshire, focuses on geometry. Its designs decrease the angle at which the foot rests in the shoe, essentially trying to make a three-inch heel feel like a one-inch version.

The two companies have rolled out podiatrists and orthopedic surgeons to testify to the comfort of their wares. They have incorporated technology gleaned from military footwear, ski boots and hiking shoes. They have sent their pumps out for biomechanical testing in order to measure stability, cushioning and the rate of impact absorption. One male product developer has even clomped around his neighborhood in a pair of size 11 heels to get a firsthand understanding of what it means to walk in a pair of two-inch sling-backs.

The idea for Insolia was born a few years ago when a woman issued a challenge to her podiatrist, Howard Dananberg, who had dabbled in shoe construction. So, Mr. Bigshot, she said, since you helped make sneakers so comfortable, make me a comfortable high heel.

"Is it possible?" Dananberg asked himself. "In the beginning, I thought no. . . . But I didn't exactly know why heels hurt."

So Dananberg put on a tie -- to look like a researcher rather than a lothario -- and stood on the corner at Lexington and 48th Street, not too far from Grand Central Terminal, and stopped women on the street. "I said, 'Can I ask you a question about high heels?' "

"There was a segment that said, 'If you touch my shoes, I'll kill you.' "

Finally, though, he learned that high heels mimic the dynamics of walking downhill. "When you stand in high heels, it's like a ramp. All the weight goes to the ball of the foot," he says.

Runway models, with their backward-tilting torsos and galloping-horse gait, have learned to accommodate four- and five-inch heels by doing a balancing act. A woman's pelvis -- broader than a man's -- helps to put a sway in her gait that allows her to negotiate high heels. "In-shoe" pressure testing helped Dananberg analyze how the foot bears weight inside a shoe. And he began to wonder, "What if I shift the weight back and create a balance closer to 50-50? A balance like when you're wearing flats?"

Working out of his Bedford, N.H., office, Dananberg began bouncing ideas off some of the area's old-timers, people who used to work in the footwear business when nearby Manchester was a shoe manufacturing capital. They puttered with old lasts, modifying them, testing them and trying again.

Dananberg's secretary, a size 7, served as guinea pig. "I'd put it down and come back to it. It was expensive and I was funding it myself and I had to pay attention to my actual business," the doctor says. Finally, though, he felt he got it right. "This is not a pad," he says. "You can have heel height, pointed toes, all the looks. But no ankle instability. It balances your posture."

"And my wife always says, 'Tell how your butt doesn't get tired.' "

Feet First

Insolia technology is currently used by the Amalfi brand, known for its attention to comfort. A pair of Amalfi pumps created for Nordstrom sells for $139.95. Pricing is determined not by Insolia but by the manufacturers. Oh!, by contrast, is an actual line of shoes available for the fall, both online and at independent retailers.

The technology in Oh! shoes was developed by Mark Joseph, a self-taught product designer living in Aspen, Colo. Through his company, Comfort Products, Joseph has worked on everything from ski boots to survival gear to Easy Spirit dress shoes. He grew up in Berkeley, Calif., and he says he has spent his life "trying to make people more comfortable."

Over the years, Joseph determined that shoes can provide two kinds of comfort. They can offer short-term pleasure -- that immediate sensation of relief that comes from a generously padded insole. Or they can provide long-term satisfaction, which means that legs, knees and back aren't exhausted at the end of the day.

"Lots of shoes are good at instant gratification. But that's not based on technology. That's touchy-feely," he says. Oh! shoes involve a lot more than padding, he says.

To understand how to build a better set of heels, Joseph walked, if not a mile, at least a few blocks in a pair. He bought a few sets of size 11 two-inch heels. He strolled Aspen's alleyways. He did not wear a dress, although "it was nice seeing how nice my calves looked."

"I was hobbled in about five minutes," Joseph says. "When I started to walk around in the shoes, I felt all the forces: the impact of the heel when it strikes, the leverage exerted to push the foot down towards the front of the shoe.

"It was such an eye-opener for me to put them on," Joseph says. "Women have to change the way they walk."

Joseph made several adjustments that he can explain in great scientific detail -- the kind of stupefying but important minutiae that would have a customer's eyes glazing over in about 30 seconds. This, Joseph admits, is one of company's marketing hurdles. Oh! shoes have a molded heel, an anatomically welcoming footbed and space-age this and that. Most important, Joseph inserted shock absorbers into the heel while simultaneously increasing the shoe's side-to-side stability. The shoe flexes easily from front to back, but try grabbing it by the heel and the toe and twisting -- it barely budges. The result is a shoe that gives the body a soft landing but doesn't wobble. And instead of stitching the shoe together by hand, Oh! relies on computer engineering for consistency.

A computer-made shoe contradicts all the romance the fashion industry uses to sell footwear. Consumers are told tales of fourth-generation cobblers in Florence who lovingly assemble shoes by hand the same way their ancestors did. The fashion industry emphasizes the artisanal touch and the notion that only the human hand can mold and stitch a pair of shoes that truly understand the body.

"Where else in our world do we do that?" Joseph complains. "A fourth-generation cobbler can make something beautiful, but if it's not backed up with technology, you get behind."

Once Oh! had its first commercial line of shoes, Gary Wells, in charge of product development and a veteran of Nike and Cole Haan, sent them out for testing. "We had done lots of lab testing but we had never tested a production-ready shoe," Wells says. "We wanted a real-world test, a lab test, to compare them with traditional street shoes and running shoes."

He sent the shoes to the Orthopedic Biomechanics Laboratories at Michigan State University, which focuses on osteoarthritis research: joints, cartilage, impact, injury. They also test shoes.

Ray Fredericksen, the chief shoe analyst for Runner's World magazine, does his laboratory testing at Michigan State. Last year, he tested the Oh! shoes using machines and volunteers to measure flexibility, the energy expended walking in them, the force of impact on the body and stability. High speed videos revealed how much excess motion the shoes allow.

Fredericksen has been in the business of biomechanics for 20 years and he has tested thousands of shoes. He has tested heels before -- a pair from Wolverine Worldwide -- and the problem is always heel height. Just going from one to two inches significantly changes the pressure on the ball of the foot. He has talked to manufacturers about how to create an exquisitely comfortable pair of shoes. The conversation begins something like this: "You need to increase the depth of the shoe and broaden the heel. And cut the heel in half." Usually he doesn't get any further than that. "It all depends on how much you're willing to sacrifice fashion for function," he says. "It's always a conflict between fashion and function, and in my experience, fashion always dictates function."

When Fredericksen put the Oh! shoes and their wearers through their paces, he looked not so much like a scientist in a white lab coat but like a track coach in a polo shirt, running shorts and sneakers. The heels, in Fredericksen's estimation, did well.

"I was surprised to see them dampen or disperse the forces similar to the way an athletic shoe would," Fredericksen says, "not that I think you should run in high heels."

New Highs

Three inches is the tipping point. Put on a pair of heels higher than that and no amount of currently available technology can help.

The perfect high heel, at least for the moment, still has glitches.

"When you get over three inches, it gets tough," Dananberg says. "As a podiatrist, I'm not recommending that. But I also understand the real attraction of heels to women."

Insolia's technology can be incorporated into any style of shoe, but it changes the "DNA of the shoe," Dananberg says. A manufacturer will have to tinker with the last, which is the soul of the shoe. It's a dangerous thing to mess with the soul. Oh! is still working on the aesthetics of its shoes, trying to elevate them from nice-looking toward something closer to intoxicating. It doesn't expect to compete in the rarefied world of $500 gourmet delights created by brands such as Christian Laboutin, Manolo Blahnik, Jimmy Choo, Michel Klein and Sergio Rossi. Priced at just under $200, Oh! shoes are targeted toward "the professional working woman, lawyers, senators, bank executives," says Wells.

Still, the largest number of questions in focus groups about the shoes were fashion-related. "Most women in the groups were higher-end consumers. They were coming in wearing Prada and Manolo Blahnik. They considered the [Oh!] shoe more mature and tailored from where they were coming from," Wells says. As a result, "the spring line is much more contemporary and a little bit more fashionable."

Still, these shoes don't elicit coos. They are not particularly streamlined, needing a substantial heel to accommodate the shock absorber. They look thick rather than graceful -- not orthopedic, but not quite cool, either. They are feminine, but not sexy. Comfortable, but still not perfect.

Prada mules with four-inch heels will carry their wearer to the pinnacle of fashion but probably not comfort. New heels from Mark Joseph, below, and Howard Dananberg aim to soften the blows high fashion transmits to the feet. Howard Dananberg with an example of his kinder, gentler footwear. Top right: Amalfi sling-back with Insolia design.Shoe designer Mark Joseph, ready to go that extra mile in a woman's pumps. "It was such an eye-opener for me to put them on," he says of high heels.Old school: Feather-trimmed mules from Prada. Left and right: Impact-dissipating Mary Janes and sling-backs from Oh! shoes.