The One Punch workout is an anaerobic, fast-paced strength and power-orientated workout. It won't feel like much doing the first set or even the second but as your muscle temperature rises and the on-board ATP stores are depleted you are going to feel the burn. Your mission is to maintain the pace throughout so as your muscles get more tired your pace and output do not slacken.
Extra Credit: Reduce rest time to 60 seconds.