The eclipse thing at the gym (it's like running but smoother there is a platform for each foot and it kind of makes ovals so it's like a smoother running with out picking up your feet)has a setting that works your butt plus thats cardio so not only do you focus on your butt but you also burn a lot of calories. When I go on it I burn about 13-15 calories per MINUITE! I think it is so much easier then running but you burn more calories. Just play around with the settings to get to a good level of difficulty and to target the butt it should say what to do on the machine (on the one I use it's called plan 5)