Enlarge By Jack Gruber, USA TODAY Sales of toning shoes such as these Skechers are booming, with women accounting for 90% of a market projected to reach $1.5 billion this year. THE GREAT SNEAKER DEBATE THE GREAT SNEAKER DEBATE USA TODAY readers on Facebook have been weighing in whether toning sneakers, such as Skechers Shape-ups, really work. Here are a few of the comments from our fan page. "I wondered about them, so I tried a pair of them on. The only thing I could see that was good about them is that the heel is not higher than the ball of the foot. I was not impressed."

-- Mary Robbins "I get out and walk 30 minutes a day during my breaks at work. I definitely feel them working my legs and lower back..." -- Kim Ybarra "It's a farce! It's designed for lazy people who claim that they don't have 15 minutes a day to do a little work out, but can take a 30 min drive to Micky Ds" -- Eric Paramo "Love my Skecher Shape-Ups. I don't know if they've made a difference in exercising, but they have really helped my posture. You put them on and because of the way they are designed, your center of balance is immediately noticeable and you stand differently, i.e. better." -- Lori Berry "I don't know if they work or not, I simply can't get past the way they look! I would rather run than wear funny footwear any day."

-- Tanya Pope (Compiled by Molly Jasinski, USA TODAY) They are, advertisements say, a game-changer in athletic footwear: sneakers that are supposed to tone muscles, promote healthy weight loss and improve the posture of those who walk, work or shop in them. The makers of "toning shoes" say the shoes can help give wearers more shapely butts, legs and abs, often without the need for gym workouts. That's partly why toning shoes — which often have a rounded sole like a rocking chair, to stretch the wearer's leg muscles with each stride — represent the fastest-growing segment of the $17 billion-a-year athletic footwear industry. It's a market driven by a customer base that is 90% women, according to sneaker analyst Matt Powell of SportsOneSource. YOUR HEALTH: 'Rocker' shoe put to the test Busy moms and working women who spend much of the day on their feet — such as teachers, nurses, hairstylists and restaurant servers — are among the most devoted buyers of toning shoes, which typically sell for $100 to $250. Skechers, the market leader, now has Pro Football Hall of Fame quarterback Joe Montana touting the shoes in an effort to attract men. Powell predicts that sales will explode 400% this year, to more than $1.5 billion. "We've never seen a category grow this fast," he says. But now a growing number of doctors are warning that toning shoes don't deliver on their marketing promises and could cause injuries by, among other things, changing a person's gait, or way of walking. Claims that toning shoes can significantly contribute to a person's fitness are "utter nonsense," says Barbara de Lateur, distinguished service professor of physical medicine and rehabilitation at Johns Hopkins University's School of Medicine in Baltimore. De Lateur and other doctors warn that toning shoes create their advertised benefit by destabilizing how a person walks and say that wearing the shoes can result in strained Achilles tendons. De Lateur also says the shoes can be a particular problem for older consumers or those who have difficulty keeping their balance. Alison Drury of Louisville can attest to that. She says she broke her right ankle after awkwardly rolling over the outside of her foot during her first mile-long walk in Skechers Shape-ups shoes. "I'm afraid to ever put them on again," Drury says. Montana said in an interview that his Shape-ups walking, cross-training and running shoes helped relieve pain in his knees and back and enabled him to start jogging for the first time in 15 years. As for people getting hurt or doctors' warnings, the four-time Super Bowl champion says he can only talk from personal experience. "I haven't fallen off one yet. And I've been jogging and walking for a long time in them," he says. "I can understand people's thoughts. But once you get in, and get yourself comfortable and used to the feel and the shape of the shoe, you don't even notice it." A bright spot in the market Toning shoes try to replicate the gentle, heel-to-toe motion of walking on a soft, sandy beach. The instability built into them makes a wearer work harder to maintain his or her balance — effectively giving muscles a more rigorous workout, shoe companies say. This notion is explained in the instructional booklet and DVD that accompany Skechers Shape-ups. The basic concept of shoes that result in the wearer's heels being lower than their toes is not new. Remember the Earth Shoe phenomenon in the 1970s? But the sales and marketing by toning shoemakers such as Skechers, Reebok, MBT (Masai Barefoot Technology), Avia and New Balance are thoroughly 2010. A growing number of companies, such as Skechers and Reebok, are moving beyond clunky-looking walking shoes and rolling out sleeker-looking toning sneakers for running, training and hiking that look more like athletic than orthopedic shoes. Other companies, such as FitFlop, are rolling out toning sandals and clogs. Toning shoes typically sell for more than basketball, running or cross-training shoes. That has made toning shoes a bright spot for manufacturers and retailers in the otherwise flat athletic footwear market, in which overall sales slid 1.4% in 2009, according to the NPD Group. The only thing bigger than toning shoes' sales growth might be the claims their marketers make about them. The Skechers website says Shape-ups will help you "Shape Up While You Walk" by toning your butt, leg and abdominal muscles, burning calories, fighting cellulite, improving your posture and circulation and reducing knee joint stress. "Get in Shape Without Setting Foot in a Gym," Skechers claims. Reebok, on its website, says the balance-ball-inspired technology used in its EasyTone shoes generates 28% more muscle activity in the gluteus maximus muscles of test subjects and 11% more in their hamstrings and calves. "EasyTone shoes help tone your butt and legs with every step," Reebok says. MBT says its "Anti-Shoe" will "tone muscles your trainer never knew you had." In the movie The Joneses, Demi Moore plays a sexy suburban mom who makes the other housewives desperate for her MBTs. 'Sorry, I don't see it' There are elements of truth to the ads, according to doctors who have questioned the effectiveness and safety of toning shoes. But many of the doctors want more independent studies on the shoes, rather than industry-financed research. Other doctors, such as de Lateur, say they have seen enough to conclude that the shoes mostly represent hype. Her colleague at Johns Hopkins, Wendy Shore, says consumers would get the supposed health benefits of toning shoes and save money if they skipped buying the shoes, then "bought one less bagel a day — and walked an extra block." David Davidson, national president of the American Academy of Podiatric Sports Medicine, says the shoes basically make adults learn to walk, or run, all over again by changing their gait. That's a "scary" prospect for someone with a "borderline problem" they might not know about. Davidson says he's suspicious of any shoes that come with an instructional booklet and DVD. "Nothing about these shoes has any redeeming value to me," he says. "Sorry, I don't see it." Bryan Markinson, chief of podiatric medicine at Mount Sinai School of Medicine in New York, says some of his patients who are "not in the greatest of shape" have inflamed their Achilles tendons while wearing toning shoes. People thinking of buying them, he says, should begin an "active stretching program" or else risk injury. Jonathan Deland, chief of foot and ankle service at the Hospital for Special Surgery in New York, warns the shoes can be "dangerous" for people with balance problems. On the other hand, Deland acknowledges that he has worn Shape-ups and likes the way they make wearers use their muscles more to maintain balance. "I don't want people to think these toning shoes are like going to the gym and feeling like you did a really great workout," Deland says. "Can they help a bit? Yes." Limits encouraged Manufacturers point to thousands of unsolicited testimonials they say they've received from customers who report their shoes toned their legs and buttocks, reduced their waist or dress sizes and helped alleviate foot injuries such as heel spurs and plantar fasciitis. Jennifer Weiderman, vice president of Skechers' Fitness Group, says she doesn't know of any customers who've injured themselves. To get used to them, people should wear them 25 to 45 minutes a day for the first couple of weeks, she says. "It's like any new exercise program or eating plan," she says. "You don't want to go into it like gangbusters." As for toning shoes' critics, she suggests they try a pair before making up their minds. "We've had a lot of podiatrists, also chiropractors and medical professionals, who think they're great," she says. As with any new category, she adds, "There's always people who will have opinions." Regarding Skechers' claim that consumers can get in shape without setting foot in the gym, she says that's meant more for people who don't have the time or money for often-pricey gym memberships. "So if you can't get to the gym, you still can incorporate fitness into your lifestyle. I believe that's the premise behind that line," she says. Robert Forster, a physical therapist in Santa Monica, Calif., was hired by Skechers to research the effect of Shape-ups. His conclusion: The shoes are a good way to "increase calorie burn and activate more muscles" while walking or doing daily errands. All shoes change a person's gait, Forster says, adding that Shape-ups can improve a wearer's gait. However, people with balance problems or tight Achilles tendons should take a "cautious approach," he says. With air-filled pods on the bottom that sink into the shoes as the wearer walks, Reebok's EasyTone shoes look more like regular sneakers than the rounded-bottom Skechers Shape-ups. Katrin Ley, Reebok's head of brand strategy, predicts the company will sell more than 5 million pairs in the USA this year — and a total of 10 million globally, because the brand is making strong inroads in Europe and Asia. "It's something that is relevant around the world," Ley says. Bill McInnis, head of Reebok's Advanced Innovation division, says the company sees EasyTones as "part of an active lifestyle," not a substitute for one. "We're not trying to say, 'Hey, this is a magic bullet. You don't have to work out again.' " Not every athletic footwear maker is sold on toning shoes, however. Industry leader Nike has no plans to sell such shoes and is scornful of the products on the market. "Our focus is on creating performance products that really work," Nike spokesman Derek Kent said in a statement. "Unlike today's toning products, we won't ask the consumer to compromise on stability, flexibility or any other key performance characteristics as they train." Mixed reactions Such criticism might slow, but won't stop, toning shoes' popularity and sales growth, sneaker industry analyst Powell says. Despite the reluctance of many men to buy a product that some see as "women's shoes," he expects sales of toning shoes to men to eventually become 25% of the market. The reaction of consumers who've worn the shoes runs the gamut. Lisa Nosseir of Monroe Township, N.J., loves the "support and comfort" she gets from Shape-ups, although she thinks the toning claims are "far-fetched." Barb Likos of Denver says she considers her toning shoes a "cute gimmick." Her Shape-ups help to strengthen her calf muscles, she says, but did nothing to tone her butt and thighs. Even though they are her "most comfortable pair of shoes," she says she regrets spending $120 on them. As for Skechers trying to persuade men to buy them, well, good luck with that. "My husband would not be caught dead in these things," Likos says. If anyone's looking for a slightly used pair of Shape-ups, they can contact Drury in Louisville as she recovers from her broken ankle. "They were only worn for like 20 minutes," she says. "I would give them a great deal." Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. 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