Calorie burn lower than expected

I thought I'd run this past all you smart people.

In the absence of an HRM that calculates calories burned during workouts, I'd been using the MFP estimates. I finally got a Polar F4 a couple of weeks ago, and I was surprised to find that it gives me a considerably lower number than I get from MFP. It's also a lower number than other people get doing the same workouts who are my same age, size, etc. I work my butt off and don't even remotely slack, so I'm wondering why the lower-than-expected readings.

I got to wondering if someone with lower blood pressure also has a lower heart rate when exercising. My BP typically is about 85/55. I'm in good health, and the doctors say it's nothing to worry about, although it is a bit unusual. Then I got to wondering if my heart rate is low but my exertion is high, does that mean I may be burning more calories than the HRM indicates?

So I figured I'd toss it out there and see if anybody has some knowledge or even some educated guesses on the subject. Thanks!

i am interested in responses to this too because I am in the same situation - ...

You might want to consider meeting with a trainer. That was they can assess your zones. In certain Zones 1-3 you are burning fat calories typically, and zones 4 and 5 are your AT (anaerobic threshold). If they can put you on the treadmill and measure your heart rate accurately, that will give you a lot more accurate calorie read outs.

GOOD LUCK! :-D


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I would go along with what the HRM is telling you.
My HR resting is usually about 50. When lifting weights, running etc my HR can be anywhere from 80's (lifting) to 160's (running).
And sometimes when lifting for 30 minutes it almost seems pathetic at what the small amt of calories burned, but just going on the lifting, its not cardio, so the numbers aren't necessarily going to be too high.
I don't know of any other way that you can actually know how many calories you are burning and your HR, so I'd use what you've got?

I had the same thing when I bought my HRM. I also have the F4. I agree, what is on MFP is an estimate, and I would go with the HRM. I know it is disheartning....... but hey, best you know the truth!

Thank you Azdak for that response!!!

I've been struggling with what my HRM tells me as well (I have an F4). Like the original poster (and others) the calorie burn estimates seem low. In fact, when trying to maintain my weight, I've found using the estimates useless in determining how many calories I need a day because I actually need more than my HRM tells me I've burned to come close to maintaining (and I'm talking up to 500 calories more a day since I have a tendency to workout quite a bit and very intensely). So thank you for that explanation. Now I feel I know how better to use my HRM than I did before. I will continue to ignore what it says about how many calories I burned when calculating how many calories I need to eat (and just listen to my body as best as I can) and, instead, use it as a pure fitness tool.

MFP's estimates are not based upon your size, etc. They are general numbers put in by members who are of different shapes and sizes, and who work out from very light effort to athletic level. It's just a general number. The HRM is the way to go.

This is not true.... the exercise database will be based on your height, weight and sex here - as a member you can create and add your own exercises too, but those will not be available to other members here to use- they will be seen solely by you in your exercise section only.

I have the same issue. I have been taking a spinning class for more than a year now. I first signed up for it because it was advertised as a class in which you could burn 700 calories in 45 minutes. One day the instructor brought in heart rate monitors for everyone to try, and I only burned about 350 calories. I don't think anyone in the class actually burned 700, but most were in the 400-500 range. I think it probably has to do with many factors, including age, weight and blood pressure (I also have low BP). I try to allow for it by working out more and never consuming all the calories MFP claims you could eat and still lose weight.

I have the opposite problem. I just purchased a Timex HRM this weekend. My monitor says I am burning more than what the machines indicate. This has been a subject of concern for me this week.

Exactly what I was going to say. I have a Timex also and for my P90X workouts I burn anywhere from 550-900 calories in 1-1.5 hours. That HRM came with a test to find your Max HR but I didnt follow it because it said my Max was 164 :huh: . Even during the "non-cardio" workouts for P90X my heart rate can get up in the 170's... I entered the following stats to set up my HRM:
Weight: 127
Max HR: 191

Which means that the calorie count is only useful as a relative gauge to compare similar workouts over time. In other words, if you burn say 200 calories in 20 min on an elliptical, then in a couple of weeks burn "250" on the same machine in the same amount of time, that would be an indicator that your fitness level has improved.

Is this true? I have been thinking that my heart rate runs so high during exercise because I am still not in great shape and that as I continued to get in shape I could sustain lower heart rates during the same activities I am doing now. Basically, the more I got into shape the less calories I would burn during exercise... :huh: Am I way off here? I am sooooo confused since using a HRM. I was soo excited at first because I was burning tons of calories in my workouts, but I can't help but keep second guessing EVERYTHING - "What should my zone be?, Is my HR too high?, What is my Max HR? How do I get a GOOD workout in with a HR below 160?, Am I really burning that many calories?" :explode:

Which means that the calorie count is only useful as a relative gauge to compare similar workouts over time. In other words, if you burn say 200 calories in 20 min on an elliptical, then in a couple of weeks burn "250" on the same machine in the same amount of time, that would be an indicator that your fitness level has improved.

Is this true? I have been thinking that my heart rate runs so high during exercise because I am still not in great shape and that as I continued to get in shape I could sustain lower heart rates during the same activities I am doing now. Basically, the more I got into shape the less calories I would burn during exercise... :huh: Am I way off here? I am sooooo confused since using a HRM. I was soo excited at first because I was burning tons of calories in my workouts, but I can't help but keep second guessing EVERYTHING - "What should my zone be?, Is my HR too high?, What is my Max HR? How do I get a GOOD workout in with a HR below 160?, Am I really burning that many calories?" :explode:

The problem is that all the hype and marketing surrounding HRMs and their estimated caloric burn function has obscured the actual physiological facts. People now think that HR is *directly* involved with rate of caloric expenditure, which is not true at all. HR is only an INDIRECT indicator, and is only really accurate under certain conditions--i.e. steady-state aerobic exercise--and then only if accurate setup data has been entered.

Let me try to explain: If you are running 6 mph, the aerobic cost of that activity is approx 10 METS (a MET is a unit of intensity). Your hourly caloric burn rate is roughly the MET value of the exercise times body weight in KG. So, someone who weighs 80 Kg will burn roughly 800 Cal/hour running at 6.0 mph (outside).

For a beginner, or less fit person, running at 6.0 mph might represent 80% of your maximum. At 80%, your heart rate will be quite high, it will seem like hard work, and you may not even be able to keep up the effort for more than a few minutes.

After 6 months of training, your fitness level should improve. Now, running at 6 mph may only represent 65% of your maximum. It may seem fairly easy, your HR will be lower, your average HR for the workout should be noticeably lower. However, the aerobic cost of the activity is STILL 10 METs. And, if you weigh 80kg, you would still burn roughly 800 Cal/hour.

Unless you change your VO2 max number on the HRM, the HRM will show that you are burning significantly FEWER calories running at 6.0 mph. But that is because the HRM thinks you are running at a lower intensity because it is still working off the lower VO2 max number.

Let's use some real numbers. If 10 METS is 80% of max, the aerobic max is 12 METS. If you programmed that into an HRM, put in your Max and Resting heart rates, and then it so happened that running 6 mph put you at 80% of your heart rate reserve, the HRM should estimate caloric burn at about 800 Cal/hour, give or take 5%. As you improved your fitness level, if 6.0 mph now is 65% of your max heart rate reserve, the HRM would now think you are working at 12 METS x 65% or 7.8 METS, which would translate into 624 Cals/hour. But the cost of the activity hasn't changed--it just represents a lower percentage of your maximum than it did before. The HRM does NOT know that 10 METS is now 65% of your maximum (instead of 80%) unless you tell it.

Again, heart rate is only an indicator of the PERCENT OF MAXIMUM you are working--it does not represent a fixed rate of calorie burn. Assuming a constant weight, someone who is working at 70% of their maximum could burn 500 Cal per hour at one time, 550 Cal/hour some months later, 600 Cal/hour some months later than that. Most untrained people can see an increase of about 20%-30% in their aerobic fitness capacity (VO2 max) over time while following a well-structured aerobic training program.

As your fitness level improves, you should be able to do MORE work and thus burn MORE calories at any given submaximal heart rate. In the examples I have been using, the person who started at 6.0 mph should be progressing and now running at 7.0 mph, and thus burning more calories, not fewer.

There is a lot of talk about this idea that if you do a certain activity and intensity over and over, you will burn fewer and fewer calories. There may be some truth to that statement, but it cannot be a significant amount. I don't have time to go into that in more detail. Suffice to say that the energy cost prediction equations from the American College of Sports Medicine make no mention nor do they include any provisions for adjusting results based on long-term adaptation to an activity. It's kind of absurd actually to think that one would do the exact same intensity over and over again over the life of a workout routine.

Now, you might be reading this and saying "wow, this is a lot more complicated than I thought".

Well....yeah, it is. Which is why I sometimes get a little snippy when I read statements like "HRMs are the ONLY way to accurately count calories", and I get frustrated when I read stories of how people are spending good $$ on cheapo knockoff products, or even on models like the F4, thinking they are getting something that they are not.

Even the best HRMs--like most Polars and Suuntos--have some big limitations and require a certain level of knowledge and understanding to program them properly to get the most accurate results. As I have said before, unless you have a top line Polar RS800X or Suunto T6c (the $350-$400 models), the best accuracy you can expect from an HRM--even a good one--is within 15%-20%. And that 's OK, because you can't calculate your BMR or calorie intake with any greater accuracy either.

Azdak, thank you once again for providing that information. The way you explained it now makes SO much sense to me. I can't possibly describe the levels of frustration I have been at watching my calorie burns on my HRM decrease as I get fitter and fitter...and how I've felt that some of my favorite workouts are no longer 'effective' because I'm not burning as many calories. Thank you for describing what is going.

Like PJilly, I have constantly been adjusting my caloric intake down. It has been very frustrating to think that the more fit I get, the less I need to eat!! I have been feeling for a couple of months that eating less is having a very adverse effect on both my workouts AND my weight (even though I'm maintaining within five pounds). I have been hungry all of the time, and I show it in my mood/demeanor. I've been telling myself that I need to eat more, but that's hard to do when staring at a hard number on a HRM. In other words, I convinced myself to trust my HRM over my body because I am prone to over-eating (hence why I'm on MFP) and felt I was just looking for excuses to eat more. Based on your posts, I finally feel free to eat again....not over-eat, but eat what I think is appropriate given my level of activity (I workout twice a day very intensely). So....thank you!!

I have the f6 and mine is pretty close, within a few calories to MFP. However, in relation to your question Jill, I find i burn 30-60 more calories doing a workout if I drink a 1/2 caf mocha before hand, then doing he same workout with a decaf. My heart pounds from a 1/2 calf (I don't normally drink caffeine) so I could see having low blood pressure effecting the reading on the HRM.