This workout is designed to increase your basil metabolic rate. Meaning, you will burn more calories at rest. It is for taxing the anaerobic energy systems which means you are working out at a heart rate higher than 85% of your max heart rate. This also means that you need to burn your stored glycogen to fuel this workout. When you are working out at a level this intense you cannot go for very long. Here's the good news, it is only 16 min of hard work plus a warm up and cool down! Wow I can get behind a 16 min workout!