So, you say you want to burn the most calories possible in the shortest amount of time, and you can’t spend a lot of money on gear. The solution: Buy a jump rope—and use it. Every time your body leaves the ground (also known as plyometrics), you engage large muscle groups, such as the glutes and hamstrings, and spike your heart rate. That amounts to a high-intensity, cardio workout that can lead you to lean, ripped glory. The following workout tests your coordination, cardiovascular endurance, and courage. How tough are you? Let’s find out!