Might consider Interval training, if the goal is for maxium fat burning/muscle sparing in a relative short time. The stamina (endurance+strength) is also gresatly increased, all leading to a outstanding cardio workout. The VO2max (aerobic capacity) is upgraded to a much higher level, which would suggest that the body has the ability to burn fat even as it's at rest during the day. Any machine is not required, though a machine does have it's advantage. Can accomplish much in the way of cardio training with just a BB, DB, jump rope or just bwt weight exercises. Running (sprints) come to mind also. Usually Interval training is along the lines of 20 second maxuiym effort with a 10 second rest period to follow. And than back to another cycle of 20 second max effort, rest, etc. 4 to 8 cycles are the norm for these workouts. Different Interval systems very some in length of intense muscle action and the shorten rest period between each. Tabata, Tremblay and HIIT protocols are a few of these interval training programs. Good Luck.