I order the slave to do a workout while I watch him closely - and humiliate him! I want him to be fit enough to serve me - and to make it even harder for him, I'm going to sit on his face in between his workout. He's already exhausted, so it's much worse for him than usually! But of course, even that's not mean enough for my taste - so I tell him that I won't get up - if he wants to breathe, he'll have to lift my full weight up in between! The loser has to fight for every little bit of oxygen!