Fucking is great exercise, have not seen a treadmill used like that before, getting fucked hvile running on a treadmill is very good motivation to keep on running and running, Being on top riding a cock is very good exercise also, If you want a nice ass get on top and start riding cock, its ass training, I worked out fine for my ass, if you want a nice ass without going to a gym get on top and start to riding, the treadmill fucking is something that would be fun to try out with a guy with a big cock standing behind me, first time I seen someone get fucked while running, It's a fuck machine