Skechers, Reebok, New Balance and other brands have done a bang-up job marketing shoes with rounded soles for toning the legs and butt. But do they really make a fitness difference for Kim Kardashian, Joe Montana and friends? The New York Times and a growing body of research says, frankly, no. Studies conducted separately at the University of Nevada, Las Vegas, the University of Wisconsin-La Crosse, the University of Puget Sound in Washington and the University of Calgary in Canada have reached the same basic conclusion: The muscle activation and oxygen consumption generated by wearing these types of shoes don’t significantly differ from that produced by ordinary walking or athletic footwear. Some research has noted strength gains for small stabilizer muscles but not the big, sexy calf and glute muscles — and the effects are limited by the body’s ability to adapt and revert to the same energy expenditures that take place with normal shoes. That said, there’s little evidence to suggest increased injury risk from the shoes, so if you somehow actually like how they feel and they get you to walk more, then by all means, rock on.