Proper pacing is the key to this one. Do you go out fast on the early rounds and risk hitting the wall in the later rounds? Or find a pace that you can sustain over an extended period of time even if it is a little slower than you think you can handle early on? This was a lot tougher than I expected -- my heart rate went up and stayed up. This workout as written included a round of 15 and then back down the ladder that I scrapped as I was already dying during the round of 9.