Maybe you've seen the ads. Sneakers from Sketchers, Reebok, or MBT that claim to tone muscles, burn fat, or improve strength for people like football hall-of-famer, Joe Montana— simply by walking in them. With names like "Shape Up" and "Easy Tone," the claims of nearly effortless exercise seem too good to be true and according to one study reported in the Wall Street Journal, they just might be. Download: Please Mess With Texas