Exercise! - Burning Cals with a lower heartrate question

07-06-2007, 01:40 PM
I just got a treadmill and it says for maximum fat loss I should have a target heart rate of 138, but for aerobic a target heart rate of 155. It leads me to think that a lower heart rate will make me lose rate (a lighter workout?)...does anyone know if there is any truth to this?

07-06-2007, 02:30 PM
I'm not sure I understood, michelinwoman--is something missing in your wording?

Well, those heart rate numbers are for average people. Folks who are trained athletically often have resting heart rates between 40 and 60, which for the rest of us would be too low.

The numbers are based on maximum heart rate, which is dependent only on age, I think. So it shouldn't matter whether your resting rate is low or high, although it might take more effort to get into the correct range if yours is low. That's what I'm thinking, but I'm not sure. Maybe Meg will answer...


07-06-2007, 02:38 PM
Well, basically the short answer goes like this:

1) The fat burning zone (that lower number) will cause you to burn more fat per calorie than if you're wokring at a higher intensity.

2) The aerobic zone (the higher number) will allow you to burn more calories, but only about half of those will be fat calories.

Here's the long answer:

Aerobic Zone:

Definition: In this zone of exercise intensity, the body uses both stored fat and carbohydrates for energy. At 70-80% of your maximum heart rate, 50% of your calories burned in this zone are fats, 1% are proteins and 50% are carbohydrates. This intensity zone is excellent for increasing the number and size of blood vessels, increasing vital capacity and respiratory rate and achieving increases in pulmonary ventilation, as well as increases in arterial venous oxygen.

The aerobic phase of your workout should be of 50 minutes or less to prevent build-up of lactic acid. Always warm up with 5-10 minutes of easy pace and after the aerobic phase, cool down with 5-10 minutes at an easy pace

Fat Burning Zone:

Definition: In this zone of exercise intensity, the body uses stored fat for energy. At 60-70% of your maximum heart rate, 85% of your calories burned in this zone are fats, 5% are proteins and 10% are carbohydrates. The walker should first warm up by walking for 10 minutes at an easier pace, this burns off the blood sugar and stored glycogen so that fat-burning can begin. Walk in this zone for 30 minutes to an hour before cooling down for 5-10 minutes at an easier pace.

If you walk at a higher heart rate, you burn less fat and may kick over into anaerobic metabolism where you build up lactic acid and burn protein instead of fat once you have run out of blood sugar.

07-06-2007, 02:56 PM
Given the same period of time, you will burn more fat working out at a higher heart rate. Yes, a larger percentage of the calories burned at a low heart rate come from fat, BUT you burn so many more calories at a high heart rate, that it more than makes up for it.

Example: Working out for 30 minutes at 60% of max might burn 150 calories, 85% of which are fat (ie 127 calories of fat burned). However, working out for 30 minutes at 80% of max might burn 300 calories, 50% of which are fat (ie 150 calories of fat burned).

07-06-2007, 04:32 PM
Thanks for the great answers! I think the best way for me to start is with a "fat burning" workout. I can handle the slower pace better and therefore will actually workout...instead of finding excuses. Maybe I'll work up to an aerobic workout!

07-06-2007, 05:26 PM
well...i'm still not so sure. I know when i am in my cardio class...i work so hard that i actually have to stop and let my heartrate come back down, because it feels like if i don't, my heart my explode. and that would not be good. lol. But i seem to only have one speed....fast and furious. I can't not give 110% in class.

07-06-2007, 07:22 PM
You don't have to exercise at top speed to lose weight! In fact, if you are working so hard that you can't catch your breath, you've moved into what's called anaerobic metabolism, and that doesn't burn fat as efficiently.

When you're in fat-burning range, you don't feel out of breath even though you're probably sweating.


07-07-2007, 10:09 AM
I do HIIT 2 times per week for calorie blasting and SS the rest of the week for fat loss. (Now if I could only up my weight lifting...)

Good for you for getting a treadmill and getting fit!