Called by one reviewer as the “World’s Smallest Gym,” toner shoes are now the fastest-growing segment in the footwear industry. Shoe companies claim the shoes’ design tone legs and boost the benefits of walking. 

In fact, with well-known spokespeople pitching the product — including sports greats Joe Montana, Wayne Gretzky and Karl Malone, and the increasingly popular Kim Kardashian — the toner shoe market tripled last year alone.

Collectively, shoe manufacturers have released more than 60 different toner shoe options. The shoes seem to have become accepted by the public as a le gitimate way to stay in shape; however, recent studies say otherwise.

The American Council on Exercise conducted an independent study that showed “no evidence to support claims that these shoes help wearers exercise more intensely, burn more calories or improve muscle strength and tone.”

Additional research conducted by the Society of Chiropodists and Podiatrists support the conclusion that the shoes have minimal toning effect. Professor John Porcari, a sport science specialist at the University of Wisconsin, told the Daily Mail (u.K.) that people mistakenly think the shoes are working because of the pain they feel in their muscles when wearing the shoes. Results like this led to a class-action lawsuit against shoe manufacturer new Balance for using deceptive marketing tools to pitch toner shoes.

While the shoes’ health benefits may be uncertain, toner shoes certainly do create health risks. Consumer Reports Health recently analyzed a product complaint database and found 36 people had reported injuries associ ated with toner shoes during just three months in 2011. The number of toning shoe complaints was far greater than any other single type of product. In one ABC News report, an individual suffered a broken bone after just 45 minutes in the shoes.

Unfortunately, these injures are not surprising to many health care profes sionals, as toning shoes are designed to create instability. Orly Avitzur, MD, medical advisor to Consumer Reports Health, concluded that anyone with balance issues, back pain, neuropathy or unstable ankles should not wear toner shoes.

However, the toning shoe danger is not limited to individuals with balance is sues. Even young people in good shape have reported problems with toner shoes. A test by the American Academy of Podiatric Sports Medicine and American Council on Exercise showed prolonged use can lead to material alteration of individual walking gait me chanics. This is particularly concerning, considering the industry’s new marketing campaign push toward preteens.

In response to the Consumer Reports Health report, Skechers, a leading toner shoe manufacturer, dismissed the risk and danger to its customers:

“Like other shoes that have natural built-in instability, like high heels or roller blades or roller skates, Shape-Ups are slightly unstable. That’s what gets you the fitness benefit. But you have to follow the instructions. That’s why every box of Shape-Ups comes with written instructions and a video telling you how to use the product.”

Regardless of what the manufacturers say, be an educated consumer. Learn all you can about toner shoes and then make a decision about whether or not you want to take on the risks associated with these shoes.

– Brett Emison is a partner at Langdon & Emison in Kansas City, Missouri.