I think that the point most people missed, is jumping rope at 180 revolutions per minute. That's 3 full cycles of the rope per second, for 20 minutes. I would think most of the people who are saying that rope-skipping is a poor form of cardio are jumping in the 40-75 revolutions per minute category. It's kind of like saying Walking is a poor form of cardio. But Jogging isn't. And Sprinting is one of the best. They're all in the same school of thought, but have completely different levels of intensity. Most people 'walk' at about 50-65 steps per minute. A jog? 120 or so. Full sprint, you'd be hardpressed to keep up 180 steps per minute for longer than 3-5 minutes.