The Ring of Fire Workout

Ring of Fire is a workout comprised of a number of lower body exercises that start and finish with High Knees. High Knees, actually, form the imaginary boundary of the workout which means you'd better have those knees coming up to waist height and your heel shouldn't touch the ground while performing them. Pump your arms as well and you're guaranteed a VO2 Max load.

Extra Credit: 1 minute rest between sets.