One of the hardest things you can do is get into a ring and go a few rounds. Beyond the fact that there is the inevitable exchange of blows you are pushing your entire body to the limit with no room to ease off, no matter how much your muscles ache or your lungs burn. As a physical test the Contender takes you through one exercise after another, slowly loading each muscle group and then asking you to exercise even as fatigue tags at you. Well, there is no exchange of blows taking place, so dig deep and feel the burn.
Extra Credit: 30 seconds rest between sets.