I got a pair of the Sketcher rounded bottom walking shoes and had begun wearing them to work 4 days out of 5 to work. I am on my feet for five hours a day for the four days. My leg muscles have become very tight and well defined but my toenails are coming in double. Nothing hurts and the shoes are not tight on my feet. I can wear cushioned sox with the shoes and they are not at all binding on my feet. Is the "exercise " I get with the shoes causing the double growth?