Interval training refers to high intensity exercise followed by low intensity exercise in a continuous pattern. This technique raises your metabolism considerably and after you are done working out you are still burning calories as your body tries to recover!!! A great interval workout is a 30 second sprint followed by a 30 second jog. Repeat this pattern for 20 minutes for an awesome calorie burn. You can use this technique on a treadmill, bike, elliptical, or even a track!