A minute's worth of High Knees is approximately equivalent to running a mile provided you pump your arms back and forth properly and bring your knees to waist height each time. Gut Buster is a workout that raises your body's temperature and maintains it throughout the workout. It is important you maintain form here and add EC for that extra load on your lungs that pushes the boundaries of your endurance, further.
Extra Credit: 1 minute rest between sets.