I have tried a couple of different brands of these, and liked Reebok the best (I think because they don't look so funny - they actually look like a regular gym shoe). After walking about 3-4 miles a day in them for awhile, I did notice my calves seemed pretty toned (I'm not sure how much of this is due to just the walking itself, though). However, I don't really think they'll do much for people who just wear them around during the day (no extended walking) - the commercials like to market these shoes as some sort of miracle muscle toner, but they're not. One disadvantage is that if you do use them for extended walking, they tend to wear out fast, especially the back of the shoe above the heal, because there is constant rubbing in certain areas. After wearing out a few pairs way too fast, I went back to my regular New Balance walking shoes. So I guess overall, I would say they're not particularly worth the extra money.