High Intensity Interval Training. Can be done on a treadmill or track or any cardio machine really. AT the track::: warm up for 5 minutes, normal walk, then sprint as fast as you can for about 20 seconds, walk or jog for 40 seconds, do this about 8 times, then cool down, normal walk for 5 minutes. Another way, is warm up one lap, sprint the straights, walk or jog the curves, Do this about 8 sprints, cool down one lap. Hope this helps. You can do it very many different ways. The idea is too change it up every few minutes high, then low. Confuses your metabolism. I love it!!!!