But I guess the idea is feasible. It's like standing on one of those balance balls at the gym. And those are supposed to be good for abs or something, right? So the idea is that by making the bottom of your shoe unstable, you make all of your muscles work harder all the time, thereby burning calories, toning muscles, and earning your booty shorts.
If you want to spend $125 on a walking shoe that makes it harder to walk, that's your prerogative. But inquiring minds want to know: Do the shoes really work?
Let's start with the official shoe sites. They all offer some sort of sciencey discussions of why their shoes work. The most outrageously priced of the unstable shoes, coming in at around $250, are the MBTs. (The acronym is short for Masai Barefoot Technology, a confusing name for a shoe that puts about an inch and a half of cushioning between your foot and the ground.) They have an "Academy" that they pay to conduct their research. As they explain in a sentence I can only hope was translated from another language, "Optimisation of the effectiveness of MBT is therefore supported by science."
MBT has an extensive list of studies performed by their "Academy." Most of them have to do with posture, back pain, and knee pain, but I'm interested in whether the shoes do the job most women presumably buy them for: exercise without exercising. In one study, the shoe scientists found that their shoes did increase oxygen use and heart rate--in subjects who stood still for six minutes at a time. When walking or running, people weren't working any harder with MBTs than with regular shoes.
Reebok, meanwhile, offers a shoe called Easy Tone. I had a harder time finding the commissioned studies for this shoe, though their site does allude to "research" and testing "in the lab." (I watched the movie called "Experience Easy Tone" thinking it would explain the sciencey ideas behind the shoe, but instead it was 54 seconds of the bottom half of a woman walking through a city in underwear and sneakers while a soundtrack said "sexy sexy.")
Reebok relies mostly on testimonials: "Easy Tone shoes make me feel like I have a tight tush," says Hannah. "I can FEEL them working!!" says Sara. Perrine from France adds, "These shoes make me WANT to walk more."
So much for Reebok. On to Skechers Shape Ups. The four studies they summarize on their site have a pretty specific conclusion: that the shoes "increase muscle activity and energy consumption over standard fitness shoes!" (Exclamation point theirs.)
In the largest of the Skechers studies, 80 men and women followed an 8-week walking course. The results, which are not described as statistically significant, include 2.5 pounds more weight loss than the control (regular shoes) group; 1.3% body fat lost (compared to 0.5%); and a vague 114% "improvement" in muscles (compared to 68%). Another study did not have a control group, while a third study gives conclusions without explaining what it did. Their final study was maybe the most interesting: It measured activity in various muscle groups (calf, buttocks, back, thigh) and found that the muscles were working harder with the Shape Ups--but this effect was mostly noticeable at a pace of 3 km/hour. That's 1.8 miles an hour. If you can put on bouncy sneakers and maintain a pace that slow, you are a more patient person than I am.
Finally, here's a study done by the American Council on Exercise, a nonprofit group not paid by any of the shoe companies. They put people on treadmills in all three kinds of unstable shoes and measured their exercise response (how hard they were working) as well as the activation of various muscle groups. The results? Nada. University of Wisconisn, La Crosse, researcher John Porcari says, "Don't buy these shoes because of the claims that you're going to tone your butt more or burn more calories. That's absolutely wrong."
What about the people who claim they really feel like they're working harder? "If you wear any sort of abnormal shoes...your muscles are going to get sore," Porcari says. "Is that going to translate into toning your butt, hamstrings and calves? Nope. Your body is just going to get used to it."
It's worth noting that this study used "physically active" female subjects. Maybe people whose regular level of activity is lower would experience more muscle activation when they started using the shoes--though that's not to say they wouldn't adapt over time.
If buying springy shoes gets people excited about walking more, I can't object too much. But let's be honest about what people are actually paying for. And if I really wanted "barefoot technology," I would try those Vibrams. After reading, and very much enjoying, the book Born to Run, I was convinced that these shoes are a good idea. (For running, that is. If you want to wear them to the grocery store, you're on your own.)
Not that I've bought a pair yet. I mean, they look ridiculous.