So prepare yourself for the madness that is about to hit you. I found this core and arm workout on BodyRock.tv called Girl On Fire. It is part of their Hiit Workout Series. I tried it, and thought I'd share it with you. Please note that this involves standing upside down so if you get queasy or you feel you are not strong enough, do not attempt this workout. Otherwise, give it a go! You'll feel amazing after! I didn't do it for all four minutes, so just do as many as you can.