I was hoping someone has some more experience with this here. I filled for target heart rate on some site and it gave me two different ones. One is for my "aerobic conditioning zone" and the other is for my "fat burning zone".
My thoughts were always that if my heart rate is higher and I'm exercising at a higher intensity, I am then burning more calories/fat. So why is the "fat burning zone" lower? Is it to give me a minimum or what is it's purpose?
Any help is appreciated!
Michelle
To help explain, it you first have to understand 3 things - how " zones " are calculated and, then, what they are presumed to represent and then, why they can be misleading. What I'm referring to is the " zones " you may see displayed on your treadmill or on a wall chart on the gym wall.
How " Zones " are calculated using heart rates :
It all starts with your Maximum Heart Rate ( MHR ) - in theory, the fastest and hardest your heart can beat. You've probably seen this estimate calculated as 220 - your age = your MHR. So, if you're 30 year old guy, the MHR would be 220 - 30 = 190 beats per minute. Depending on what expert you talk to, heart rates within a certain range are called " zones ". But, what all the " zones " have on common, is that they are expressed in term of " % of MHR ". So 85% of MHR in the example above is 190 X .85 = 161 beats per minute. The examples below are not exact, but they'll do for illustration purposes, as they give you a pretty good example of what some of the generally accepted " zones " might be on any given machine or chart in terms of MHR. Again, different people will put different " exact " MHR's with each zone, but these MHR numbers you see are simply for illustration purposes only
Cardio Zone : ..............................50 - 60% MHR
Fat Burning Zone :........................60 - 70% MHR
Aerobic Zone :.............................70 - 80% MHR
Anaerobic Zone :..........................80 - 90% MHR
Maximum Zone : ..........................90 - 100% MHR
What " Zones " are presumed to represent :
They represent A LOT of different things in terms of how your body adapts to exercise, but I will simply limit describing what they mean in terms of how your body burns fuel. The thing to remember is that when your body is exercising ( or even when it isn't exersicing ), it always uses 2 kinds of fuel at the same time - fat and sugar. At each " zone ", your body is presumed to be burning a different proportion of fat and sugar. Again, different people will put different " exact " fat / sugar proportion with each zone, but these numbers you see are simply for illustration purposes only - they are not meant to be exact. So, in terms of how much fat is burned at each, it might look something like this.....
Cardio Zone : ..............................85% fat / 15% sugar
Fat Burning Zone :........................85% fat / 15% sugar
Aerobic Zone :.............................50% fat / 50% sugar
Anaerobic Zone :..........................15% fat / 85% sugar
Maximum Zone : .......................... 5% fat / 95% sugar
Why " Zones " can be misleading :
Remembering 2 things will help you understand why "zones ' are misleading.
1. to lose fat your have to burn calories.
2. The harder you exercise ( i.e the greater intensity) the more calories you burn
.
Compare the Cardio and Fat Burning zone above. Both burn 85% fat, but, because the Cardio zone is only at a 50 - 60% MHR level of intensity compared to the Fat Burning zone of 60 - 70% MHR level of intensity, the Fat Burning zone burns more calories. For example, assume you do 20 minutes of exercise. Cardio burns 200 calories - 170 calories from fat ( 85% ) & Fat Burning burns 325 calories - 276 calories from fat ( 85% ). To lose fat, the Fat Burning zone is the ' optimal choice ' simply because cause it burns more calories.....remember, harder exercise burns more calories.
Same thing with if you compared Fat Burning, Aerobic and Anerobic zones based on calories consumed ( these calories are examples only ) .....
Fat Burning Zone..............burns 325 calories
Aerobic Zone...................burns 400 calories
Anaerobic Zone................burns 525 calories
So, again, to lose fat, the Anaerobic Zone is the ' optimal choice ' over the Fat Burning Zone simply because cause it burns more calories. So, it doesn't matter that the Fat burning Zone burns 85% fat. It has nothing to do with how much fat you burn - this is the misleading part - but it has more to do with
how many total calories you burn during exercise. To lose fat , you have to lose calories. The focus is on
total calories expended during exercise.
So, the moral of the story in it's simplest terms, if you want to lose fat you have to burn calories. And when it comes to exercise intensity, the more intensely you exercise, the more calories you burn.
Hope this helps a bit.
