Many heart rate monitors, especially those incorporated into fitness equipment such as treadmills, cross trainers and bicycles, have a fat burning zone. The idea is that if you workout in your ‘fat burning zone’ you will burn more fat than if you worked out at a lesser or greater intensity. However, this is just another fitness myth that has been perpetuated by poorly educated fitness advisors the world over.
The fat burning zone myth grew from an observation that low intensity exercise used more fat energy that carb energy. Maybe also the observation that long distance runners were generally very slim did not help either.
However, physiologists studying sports science have shown that we actually burn more fat when performing high intensity exercise. This is simply because higher intensity exercise requires much more energy. High intensity training / exercise is a much more efficient way to burn fat.
Possibly the best form of intensive cardio training is bodyweight circuit training. Intensity can be increased or decreased at any time, plus it works most of the muscles, which increases your fat burning potential. A typical bodyweight circuit training routine should include: star jumps, squats, lunges, press ups, sit ups / crunches. Finish off with a stretch. With circuit training you can easily increase you work by adding more sets of each circuit, or more reps of each exercise.
Also increase intensity, with rapid star jumps and squat thrusts, as these can get the heart rate up way beyond the sluggish ‘fat burning zone’ and get you super fit as well as lean.
Possibly the biggest advantage of high intensity exercise is that workouts are shorter. Why walk for an hour when you can burn as much energy in 20 minutes do circuit training in you living room?