Do you use HRM burn?

chickybuns

I have a Polar FT-4 and the burn just seems so high, so I've been using 75%. Do you think I should use the whole amount. For example, I just did a 55 minute Turbo Fire workout and it said I burnt 715 calories. I have it set as 175 as my weight and I weight around 185. Thanks

vorgas

First of all, 715 calories in 55 minutes is not out of scope. We weren't there and have no idea how hard you worked so it's hard to say. Two people can do the same workout and burn a different amount of calories.

Next thing to understand is that your HR is not the be all/end all of calorie burns. It goes up and down based on a lot of factors.

You can easily prove this by holding your breath as long as possible. Exhale deep, breathe in deep, hold your breath again as long as you can. Do it one more time. Take a look at your HR. Notice how it's sky high. You aren't burning more calories just because you're holding your breath.

One of things that causes an elevated heart rate is stress. When you are put in uncomfortable situations your HR elevates. If Turbo Fire is new to you, or diet/exercise in general is new, your HR is going to be elevated over normal.

It's also possible that you have a heart condition, like a mild tachycardia that causes your HR to elevate during exercise beyond normal levels.

That being said, understanding how and why HR responds to aerobic exercise will help you understand the answer to your question.

When you are doing aerobic exercise your body is combining oxygen with fat to create ATP. The more oxygen your body needs the more your HR elevates. This is a fairly well studied and understood phenomenon. Using lots of different data points they are able to chart an average for a given HR for a certain gender/age/weight condition.

However, there is something called VO2 Max, which is the amount of oxygen you can efficiently suck in and process. The higher your VO2Max the lower your HR is at a given exertion. High performance athletes can get above 60 ml which is twice as high as some folks who can only process 30 ml of oxygen. That means each beat of their heart is pushing twice as much oxygen. Obviously it doesn't have to beat as fast to do the same amount of work.

So without knowing your VO2 Max, your HRM can only give a rough estimate of your calorie burn based on your HR.

Ultimately though, none of this is a big deal. Every number you deal with is an approximation.
Your BMR is an approximation.
The number of calories in a meal is an approximation.
The number of calories you burn during exercise is an approximation.

For example, depending on how long you stay in the anaerobic heart rate zone, your calorie burn can vary by as much as 30 calories because of using glycogen/protein instead of pure fat for fuel.

Your adjustment is less than 200 calories. You're talking about 5% of a pound of fat, which is less than one ounce. Over a week it still won't add up to half a pound.

heybales

I have a Polar FT-4 and the burn just seems so high, so I've been using 75%. Do you think I should use the whole amount. For example, I just did a 55 minute Turbo Fire workout and it said I burnt 715 calories. I have it set as 175 as my weight and I weight around 185. Thanks

Actually, by lowering the weight, it thinks you are more cardio fit, better VO2max. So the same HR compared to heavier setting is going to show more calories burned.

Increase the weight back to honest, and actually, do you workout naked? Full weight.

That cheaper Polar will assume your VO2max is now worse than before, and that same HR will cause less calories to show burned.

Women already have the bad end of the stick for accuracy on HRM and calorie burn estimates, don't make it worse. And this study is for the more expensive units, you'l can be even worse.

http://www.myfitnesspal.com/topics/show/459580-polar-hrm-calorie-burn-estimate-accuracy-study

And as you start out, your HR is really inflated for the work being done, so it is likely tad inflated.
After couple weeks your HR for same effort will probably be 10 bpm lower, so less burn.

chickybuns

I have a Polar FT-4 and the burn just seems so high, so I've been using 75%. Do you think I should use the whole amount. For example, I just did a 55 minute Turbo Fire workout and it said I burnt 715 calories. I have it set as 175 as my weight and I weight around 185. Thanks

Actually, by lowering the weight, it thinks you are more cardio fit, better VO2max. So the same HR compared to heavier setting is going to show more calories burned.

Increase the weight back to honest, and actually, do you workout naked? Full weight.

That cheaper Polar will assume your VO2max is now worse than before, and that same HR will cause less calories to show burned.

Women already have the bad end of the stick for accuracy on HRM and calorie burn estimates, don't make it worse. And this study is for the more expensive units, you'l can be even worse.

http://www.myfitnesspal.com/topics/show/459580-polar-hrm-calorie-burn-estimate-accuracy-study

And as you start out, your HR is really inflated for the work being done, so it is likely tad inflated.
After couple weeks your HR for same effort will probably be 10 bpm lower, so less burn.

Thanks, I will adjust the weight. I workout in my sports bra and underwear, so not much added weight...unless you count the shoes. I am just getting back into shape so I figured that's part of the reason it's higher. When I used my bodybugg it always ready around 10cal per minute, but that doesn't take into account effort.

After reading the study, I guess it's safe that I take 75%, since it can be more than 25% off....I just hate all the guessing!

heybales

Thanks, I will adjust the weight. I workout in my sports bra and underwear, so not much added weight...unless you count the shoes. I am just getting back into shape so I figured that's part of the reason it's higher. When I used my bodybugg it always ready around 10cal per minute, but that doesn't take into account effort.

After reading the study, I guess it's safe that I take 75%, since it can be more than 25% off....I just hate all the guessing!

For the BodyMedia, if the workouts are walking/jogging, it'll be more accurate than HRM usually, because calories burned on moving mass against gravity is much more reliable for range of pace, and BMF can sense that usually.