This is the formula you can follow to give you an idea of how you can train. But I must emphasize here, that you need to do this in consultation with your doctor. Minus your age from 220, to get a figure that is your maximum heart rate. This is theoretical figure. Now 65% to 85% of this figure is what you should aim for in your aerobic workout, depending on the intensity of the workout. If you are looking for a fat burning zone, you should be at 65% of this figure for a longer period . If you want to train your cardiovascular system in the higher zone, take 80% of this and that is what your heart rate should read when you are in your peak zone.