It can, as well as your running form. Basically, you do not want any sideways motion while running because it will apply a stress to your knees and ankles. If you are flat-footed or otherwise "roll in" (after your foot is planted, you shift your body weight from the center of your foot to the inside of your heel--it's easy for me to see but kinda hard to describe), then you probably need a running shoe that corrects for it. These shoes have harder rubber under your arch that does not compress as easily and forces your foot to stop rolling in. Rolling out is more rare but still a possibility, and they have shoes for that as well. EDIT: My 3-mile time is down to 26:04, and I've lost at least 5 lb. of fat. Won't be last at this rate.