According to manufacturers, the shoes function by slightly disrupting the wearer's balance, thus engaging more leg and buttocks muscles and forcing the person to work harder while walking.
"For the little bit that they do get for it, they're not worth the money," said Heather O'Neill, owner of South Pointe Fitness Club in Hagerstown.
"They're a waste," O'Neill said. "Anytime you're on an unstable surface, you're going to recruit more muscles."
A recent study released by the American Council on Exercise (ACE) found "no evidence to support the claims that these shoes will help wearers exercise more intensely, burn more calories or improve muscle strength and tone."
Researchers for the ACE-funded study recruited two groups of 12 physically active women to test the effectiveness of three shoes: MBT: Masai Barefoot Technology ($245); Skechers Shape-ups ($110 to $125); and Reebok EasyTone ($100 to $125).
Skechers, Reebok and MBT have responded to the claims in news reports by pointing to their own studies that support the effectiveness toning shoes.
The American Podiatric Medical Association has given its "seal of acceptance" to toning shoes made by Reebok, Avia, Ryka, FitFlop and Keds, according to the organization's website.
Hagerstown resident Paige D'Allura said her MBTs were the best investment she's ever made.
D'Allura, 41, said she purchased the shoes five years ago with hopes it would improve her back problems. She said she spends hours on her feet in the winter and fall because she sells goods at regional craft fairs.
"My back doesn't hurt, my legs aren't as sore," D'Allura said.
However, D'Allura said she doesn't wear the MBTs for the exercise benefits. She showed up to South Pointe for a Thursday-evening training session wearing a pair of Nike cross-trainers.
"I don't think in exercise, they have the benefit," D'Allura said of her MBTs. "I wish they did, but they don't."
According to SportsOneSource, toning shoes accounted for six of the 10 best selling athletic shoes in the United States.
"This toning thing is a huge deal, very transformative to the industry," said Matt Powell, an analyst for SportsOneSource, which tracks market and sales data of sporting goods.
Skechers USA Inc., -- one of the leading toning shoe makers -- announced record second-quarter net sales of $504.9 million, according to documents the California-based company filed with the Securities Exchange Commission.
Penny Knill, 48, of Hagerstown, said she's been eyeing a pair of Skechers Shape-ups at the outlet mall, with hopes they'll come down in price.
Knill said she has health problems that make it hard for her to maintain balance. Exercise classes, she said, haven't helped.
"I wonder if walking every day with these shoes would help improve my strength and balance over time," Knill said.