Call them toners, shapers, or rocker bottoms, those exercise shoes with the distinctive thick, rounded soles are flying off the shelves and onto the feet of even the most clodhopper-averse walkers.
And if experts differ on how effectively the shoes will buff butts and carve calves, they concur that whatever gets you moving is a good thing.
"I tell people to make your bottom half your better half," said Denise Austin, a fitness expert and spokesperson for Skechers Shape-ups. "They make you feel like you're walking on sand."
Toning shoes use curved soles and extra padding to alter the wearer's walking gait, purportedly engaging seldom-used muscles, increasing blood flow and reducing stress to the lower back.
"The second you put them on you think 'good posture'," Austin said "They make you more aware than regular shoes."
She said letters she's received from nurses and others on their feet all day praise them for their comfort.
As for exercise: "I feel it in the butt and the back of my thighs. And if a couple of more calories get burned each time you're out there, why not?"
Dr Cedric Bryant, chief science officer of the American Council on Exercise (ACE) said the instability built into toner shoes is purported to increase the workout, much like an exercise ball works the core by keeping it off balance.
"Many manufacturers promote these shoes to help tone the muscles of lower extremity, activate the core, as well burn more calories," said Bryant.
So ACE commissioned a small study at the University of Wisconsin, La Crosse to compare three brands of toning shoes to normal running shoes, using two groups of 12 active female participants.
"The results were remarkably consistent," Bryant said. "All individuals burned the same number of calories, all activated the same muscles. There was no significant difference between the two groups."
"Based upon our study, if you are looking for shoes to produce calorie-burning and muscle-toning, you can choose either toning shoes or regular sneakers," Bryant said.
Dr John Porcari, who led the study team, said any added muscle soreness is likely due to the toner's abundant cushioning.
"Is that going to translate into toning your butt, hamstrings and calves? Nope. Your body is just going to get used to it."
While those expecting the shoe to shape, tone, and burn may be disappointed. Bryant noted that podiatrists have long used one brand, MBT: Masai Barefoot Technology, to treat people with ankle instability.
Barbara Belyea, clinical associate professor of physical therapy at Ithaca College, in Ithaca, New York, described the case of a healthy 72-year-old man with balance issues who wore the shoes for 10 weeks. At the end of the trial he showed increases in lower extremity muscular strength and improved balance.
"It would be interesting to use MBTs in a large study with patients who are more frail," Belyea said.
Bryant said toner shoes have effectively brought attention to the excellent activity of walking.
"If we can get more people off the couch, that's a wonderful thing," he said.
