Let's talk about exercises that target your glutes or your buttocks. Now any lower body based exercise is going to strengthen the glutes, so for example doing a squat, or doing a dead lift, or doing lunges, or if you wanted to add a little more high intensity to any of those exercise by making them a squat jump or a lunge jump, that would be a great way of ramp up the intensity of any of those lower body moves. Now when it comes to decreasing the size of the buttocks, you would have to really kind of focus on doing more high intensity, because in that case what you're probably aiming to do is burn more fat, and the most successful way of burning more fat is to do high intensity cardio and of course to eat right. If you wanted to increase the size of your glutes you'd have to do heavy weight training and really try to build the muscle mass itself. You would be doing hypertrophy training to increase the size of the muscle. So it really depends on what your goals are. Are you trying to shrink your glutes, in which case you want to do a lot of high intensity, plyometric movements that involve the legs, again, like the squat thrust, like the lunge jump, like the split stands jump, like walking lunges, or are you trying to build mass, in which case you can do any of those movements, but at probably a lower speed and greater amount of weight. You'd have to add some sort of load if you wanted to increase muscle mass.