If you've taken the subway recently, we're sure you've seen FitFlops, the thick-soled thongs that destabilize your foot, so wearers use lower-body muscles with each step. Today, the Sun reports sales are on the rise, claiming more than a million pairs have been sold, many of which we've spotted on the feet of women in this city hoping to burn calories on their commutes.

We realize buyers are drawn to these for the "fit factor." But really, as any fad dieter knows all too well, there is no quick fix for fitness. One tester told the paper the FitFlops tightened her calves and replaced the gym for her. But how can a pair of shoes replace an entire workout? Answer: It can't. In fact, the podiatric surgeon they interviewed said: "You're going against a little more resistance, so you're going to get a little something extra, but these are not shoes that are going to make your thighs look like they did when you were 21." Brilliant revelation.

And minus the thigh muscles we may or may not get, we're not the biggest flip-flop fans. On the beach they're great, but on a dirty train or city sidewalk, we opt for something a bit more … stylish. Even the pair made exclusively for Kirna Zabête (above center) couldn't pull off the flip-flop-as-fashion look, and instead came out looking like something more appropriate for Equinox than Kirna.

But we're willing to open up the discussion. What do you think of FitFlops? Would you wear them? Have you seen them on the legs of city gals? Let us know what you think in the comments. —Sharon Clott

Stride Right [NYS]