Highway to the Danger Zone!
If you’ve ever used a cardiovascular machine at a gym, you are probably familiar with the above graphic. This colorful box is a target heart rate zone chart. You jump on a cardio machine, look at this handy guide and by simply matching your age to your goals find the perfect heart rate to work at to achieve the results you want. Sounds good in principle but in practice it is very flawed and is misunderstood in the world of fitness.
My first problem with the chart is that most of them get their information from old research originally used for cardiac rehab patients. The heart rates listed on these charts can be off by as many as 20 to 40 beats per minute depending on the population. According to this chart, yesterday I was in the danger zone numerous times during a bike interval workout but I’m still here typing this blog, none the worse for wear.
My second and main problem with these charts is the “Fat Burning Zone”. In my opinion this area of the graph has done many exercises a disservice by preventing them from working up to their full potential. Let me explain. It is true that your body will burn a higher percentage of fat calories in this zone. (So maybe it’s not a myth, but a mislead!) The problem is that at this low-level of effort you burn very few calories. So in the end you’ve burned a high percentage of fat, but very few calories which isn’t very efficient.
You are better off working harder for less time. See my post on Interval Training for a full description of how to do this and the benefits of this style of exercise. When you work harder, your body uses a lower percentage of fat for its energy needs and gets more from carbohydrate stores. But since you are working harder you burn exponentially more calories and a higher number of fat calories. Keep in mind this is a simplified explanation of a more complicated process you get the idea.
The target heart rate zone charts also don’t consider post exercise energy consumption. After most forms of exercise there is a period of time that the body will continue to burn calories at a high rate. With low intensity “fat burning zone” exercise this time period is very short. At higher intensities you body will continue to burn fat well after you’ve finished the activity.
So for your own good get out of the fat burning zone and see if you can get your heart rate up a little higher so you can get better results faster. As always, this information is geared towards healthy individuals with some exercise background. If you have any pre-existing conditions check with your doctor as higher intensity training may not be right for you at this time.
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