Perhaps the ultimate strength test position, the "Superman" sees you bend her over a desk or table, with her using it for support. Then, once you're inside her, lift her pelvis up slowly until her feet are actually off the ground, and you're holding on to her as you thrust in and out. The sheer physical intensity of this one means it's not for the faint-hearted, but can provide an adrenaline rush as you go closer and closer to your breaking point. Keep safety in mind and let her down gently as soon as your strength starts to wane, and make sure you don't pull out too much.