Heart Rate Monitor - Calories Burned Theory

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calamarione
calamarione Posts: 16 Member
in Fitness and Exercise
Forgive me but I'm an engineer so I'm wanting to understand how a heart rate monitor accurately determines calories burned. Here's my understanding:

- You start out entering your weight, height and age.
- The HRM reads bpm through the electrodes.
- Based on your dimensions and age, the HRM calculates your calorie rate via the bpm.
- Through the work out it tabulates the accumulated calories and gives you the total at the end.

So I have a problem with this. Calories are a unit of measure of energy. The HRM no where to my knowledge takes my base bpm (which for me is kind of high) into account. So how can it accurately tabulate what my actual calorie expenditure is? This works the other way too. If one's resting bpm is low, then regardless of one's weight, this calorie count may be way off.

Can anyone shed some light on this? Is using one's bpm merely an estimate based on empirical data?

Replies

  • Lizabelle1212
    Lizabelle1212 Posts: 252 Member
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    When I first got my HRM and was going through the set-up, it did take my resting heart rate as well as asked me to enter my weight, height, and age. I have a Polar brand heart rate monitor, so I'm not sure if all HRM's are the same way. Nothing will be exact, but from what I understand, HRMs are much more accurate than any other way of estimating calories burned (i.e. cardio machines, or looking up the exercise in MFP database, etc). I've been using mine for the past few months and logging my calories burned and have been losing weight, so I guess it's accurate enough! :)
  • popo312
    popo312 Posts: 78 Member
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    My guess is that it's taking your mass you input and you HR on how hard it is for you to move that mass and converts that to a calorie output. Likely much much more complicated than that but that's my guess.
  • Jruzer
    Jruzer Posts: 3,501 Member
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    My Polar RS100 has settings where I input resting heart rate and max heart rate. More basic ones may just make guesses as to those values.

    To get calories burned, I'm pretty sure they use an empirical fit of % max HR to calorie expenditure calculated via VO2 consumption. But I'm willing to be proven wrong.
  • sfbaumgarten
    sfbaumgarten Posts: 912 Member
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    Mine has resting and max HR...

    ETA: It's a Polar RS100 also.
  • brianpperkins
    brianpperkins Posts: 6,124 Member
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    Low end HRMs use more generic inputs. Higher end HRMs incorporate resting heart rate, VO2 max, adjustable heart rate zones. All then plug that data into an algorithm to translate heart rate to caloric burn. None are perfect but few of us have a full up performance lab to work out in every day.
  • hilts1969
    hilts1969 Posts: 465 Member
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    Forgive me but I'm an engineer so I'm wanting to understand how a heart rate monitor accurately determines calories burned. Here's my understanding:

    - You start out entering your weight, height and age.
    - The HRM reads bpm through the electrodes.
    - Based on your dimensions and age, the HRM calculates your calorie rate via the bpm.
    - Through the work out it tabulates the accumulated calories and gives you the total at the end.

    So I have a problem with this. Calories are a unit of measure of energy. The HRM no where to my knowledge takes my base bpm (which for me is kind of high) into account. So how can it accurately tabulate what my actual calorie expenditure is? This works the other way too. If one's resting bpm is low, then regardless of one's weight, this calorie count may be way off.

    Can anyone shed some light on this? Is using one's bpm merely an estimate based on empirical data?

    Unless you have health problems the best thing you can do with an HRM monitor is throw it in the bin, to most it is a complete waste of time, listening to your own body is the best way to go
  • toddis
    toddis Posts: 941 Member
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    There are a couple people on here that are rather knowledgeable on this subject, I'm not one of them.

    I believe they use a formula derived from gathered data from studies then make best guess estimates based off that.

    There is a thread on these forums on how to adjust your HRM to be more accurate based on your true max HRM .(fudging your age and such)

    As an engineer you'd probably understand the other idea that you can just figure out calories burned based on distance, weight, blah blah blah, as it takes the same energy regardless of heart rate? There is a thread about that too...but I can never find it.


    Found a relevant post
    http://www.myfitnesspal.com/topics/show/774337-how-to-test-hrm-for-how-accurate-calorie-burn-is

    and from same users blog

    http://www.myfitnesspal.com/blog/heybales/view/mfp-topics-of-studies-or-tips-213035
  • Mr_Knight
    Mr_Knight Posts: 9,532 Member
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    So I have a problem with this.

    You *should* have a problem with it. :smile:
    Calories are a unit of measure of energy. The HRM no where to my knowledge takes my base bpm (which for me is kind of high) into account.

    Oh, that's just the start of the problem. It also doesn't take into account your body's efficiency in actually using oxygen for "combustion", which varies *hugely* - like up to half an order of magnitude - between unfit and fit people.

    And then there's the issue that there is tons of hysteresis in heart rate response where BPM is more or less completely divorced from actual energy expenditure, which shows up all the time on MFP in the form of vastly over-estimated burns for intervaly type "cardio" workouts.
  • michellekicks
    michellekicks Posts: 3,624 Member
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    Indeed. An HRM is just a guide for rough calories burned. It's supposed to be for... you know, monitoring heart rate.
  • fleetzz
    fleetzz Posts: 962 Member
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    I don't know the algorithm but you are right.
    It is just a guesstimate. It will give approximate not exact calories and as you get in better shape and your heart rate decreases it may lower your estimate inaccurately.
    Forgive me but I'm an engineer so I'm wanting to understand how a heart rate monitor accurately determines calories burned. Here's my understanding:

    - You start out entering your weight, height and age.
    - The HRM reads bpm through the electrodes.
    - Based on your dimensions and age, the HRM calculates your calorie rate via the bpm.
    - Through the work out it tabulates the accumulated calories and gives you the total at the end.

    So I have a problem with this. Calories are a unit of measure of energy. The HRM no where to my knowledge takes my base bpm (which for me is kind of high) into account. So how can it accurately tabulate what my actual calorie expenditure is? This works the other way too. If one's resting bpm is low, then regardless of one's weight, this calorie count may be way off.

    Can anyone shed some light on this? Is using one's bpm merely an estimate based on empirical data?
  • Mr_Knight
    Mr_Knight Posts: 9,532 Member
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    It is just a guesstimate. It will give approximate not exact calories and as you get in better shape and your heart rate decreases it may lower your estimate inaccurately.

    For most people, most of the time, it will be the other way around - it will vastly over-estimate at the beginning, and get closer to the actual much-lower number as the person improves their fitness level.

    The more out of shape someone is, the more they need to discount any number out of an HRM.
  • michable
    michable Posts: 312 Member
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    My husband and I share a Garmin GPS Watch, and he never wears the chest strap to monitor his HR, but the watch still gives an estimate of calories burned at the end of a run. The watch is set up with my age, weight, height, resting HR. I think it uses my stats and works out cals burned based on time and distance.
  • michellekicks
    michellekicks Posts: 3,624 Member
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    My husband and I share a Garmin GPS Watch, and he never wears the chest strap to monitor his HR, but the watch still gives an estimate of calories burned at the end of a run. The watch is set up with my age, weight, height, resting HR. I think it uses my stats and works out cals burned based on time and distance.

    I have a Garmin Forerunner 410 with the "firstbeat algorithm" thingie... if I wear the chest strap I get a lower calorie count than if I don't. Just guessing that it is expecting my HR to be higher than it actually is at the speeds I run.
  • ibleedunionblue
    ibleedunionblue Posts: 324 Member
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    Unless you have health problems the best thing you can do with an HRM monitor is throw it in the bin, to most it is a complete waste of time, listening to your own body is the best way to go

    That's nonsense. A HRM is a great training tool, and can help me determine how hard I am pushing my heart to train more efficiently. I can glance at the watch and see its time to increase speed, or incline, what zone I am exercising in, and if my body is rest for the next interval.

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