Polar HRM calorie burn estimate accuracy - study

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  • barbaratrollman
    barbaratrollman Posts: 317 Member
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    I always leave 100 or so calories or approx 10% off when I mark down my HRM cals.

    OK...I can work with that. My head is spinning from all the acronyms, abbreviations, and numbers. I would sure appreciate some simplification of working out a more specific formula, but for now, I'm going to try your strategy of cutting 10 % off what my heart monitor reports.

    It seems to have been working for you. 65 pounds lost! That's great!
  • amanda_gent
    amanda_gent Posts: 174 Member
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    bump to read later!
  • Dubble81
    Dubble81 Posts: 90
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    I often feel like my FT80 is giving me inaccurate readings too. Today for example, it reported that I burned 500 calories by going for a 45 minute walk. Granted, I do weight nearly 190 lbs and there is a large hill on the walk... but it seems far too high. I'm glad I came across this thread and learned that it is not an exact science. I'm going to start reporting 75% of what my HRM is telling me. If it has roughly a 30% variance, I feel safe reporting the 75%.

    Thanks for sharing the info
  • heybales
    heybales Posts: 18,842 Member
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    I often feel like my FT80 is giving me inaccurate readings too. Today for example, it reported that I burned 500 calories by going for a 45 minute walk. Granted, I do weight nearly 190 lbs and there is a large hill on the walk... but it seems far too high. I'm glad I came across this thread and learned that it is not an exact science. I'm going to start reporting 75% of what my HRM is telling me. If it has roughly a 30% variance, I feel safe reporting the 75%.

    Thanks for sharing the info

    Part of the problem is the self-test for VO2max you have.

    The Polar FAQ explains correctly that it should be done each time you input lighter weight. Because even if your fitness level doesn't change, by being lighter your VO2max automatically goes up.
    And then it should be done the morning after a rest day, after good nights sleep, to get true RHR and their heart beat variability they use. Might as well let it guess HRmax too.

    If you do those things, much better chance.

    oh, and to test your settings afterwards.

    http://www.myfitnesspal.com/topics/show/774337-how-to-test-hrm-for-how-accurate-calorie-burn-is
  • Dubble81
    Dubble81 Posts: 90
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    Thanks again. I will take the test tomorrow morning
  • paulperryman
    paulperryman Posts: 839 Member
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    replying to an old thread but i can chime in with a comparison between a FT4 and a FT60
    with my FT4 i was getting some serious heart rate reading on average in the 140-165 range when doing a decent cardio,
    Bought a FT60 yesterday due to losing the sensor for my FT4 and i just wanted the extra options on the FT60

    the FT60 on first use was varying alot in readings and seemed to get stuck much like the exercise machines do where they get stuck on a reading for a few seconds then catchup. But i digress the FT60 on average was registering a 126-153 on the same exercise just 2 days ago so that can't be attributed to an improvement in fitness.

    Could that be purely attributed to the addition of Vo2 test which i got a rating of 44 (good level) and the fact you can set . of a kg unlike the FT4 which only allowed whole kg's, it goes purely on whatever you set your zone, Age, Weight and Height not fitness level and weight in parts of Kg's.

    But whats weird is even with that the end result was roughly the same 70mins for 730 calories (10-12 calories a minute)
  • sijomial
    sijomial Posts: 19,811 Member
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    Tagging to read later...
  • desigirl23
    desigirl23 Posts: 18 Member
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    Bump.
  • heybales
    heybales Posts: 18,842 Member
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    replying to an old thread but i can chime in with a comparison between a FT4 and a FT60
    with my FT4 i was getting some serious heart rate reading on average in the 140-165 range when doing a decent cardio,
    Bought a FT60 yesterday due to losing the sensor for my FT4 and i just wanted the extra options on the FT60

    the FT60 on first use was varying alot in readings and seemed to get stuck much like the exercise machines do where they get stuck on a reading for a few seconds then catchup. But i digress the FT60 on average was registering a 126-153 on the same exercise just 2 days ago so that can't be attributed to an improvement in fitness.

    Could that be purely attributed to the addition of Vo2 test which i got a rating of 44 (good level) and the fact you can set . of a kg unlike the FT4 which only allowed whole kg's, it goes purely on whatever you set your zone, Age, Weight and Height not fitness level and weight in parts of Kg's.

    But whats weird is even with that the end result was roughly the same 70mins for 730 calories (10-12 calories a minute)

    Very strange results on the HR readings being that far off, was the old sensor the clothe type all around, and if so was it washed regularly?
    Though being dirty usually leads to missing heart beats, so you get less bpm.

    Then again, it may be the newer one doing that.

    Reading of the HR won't have anything to do with any stats or figures. Those only come in to play for setting your HR zones and calorie calculations.

    So the Fitness test on the newer FT60 uses your restingHR, selection of Athlete level, and still your BMI as a basis to estimate your VO2max, which is then used in the calc's for calories.

    So the fact they ended up the same about, means your restingHR, and likely your fitness level as estimated by VO2max, are about average for a male your age and BMI.

    Now, did you do the fitness test per their FAQ? Morning after rest day? That can cause a lower restingHR, which can lead to a higher VO2max calc.

    It also means if you do a self-test, or find a calculator with potential better estimates of VO2, you can manually enter that stat and get better estimate of calories burned.

    Also, the study that came up with the formula that Polar uses for the self-test, found it starts losing decent estimates going above 45 mL/kg/min level of VO2max.

    www.ncbi.nlm.nih.gov/pubmed/16168867

    Here's another one that only males can estimate with, though it tends to be on the high side if above 45 VO2max. So perhaps take the avg of both, HRM calculated, and this.

    http://link.springer.com/article/10.1007/s00421-003-0988-y

    Then you just need a decent estimate of HRmax for there.
    http://www.brianmac.co.uk/maxhr.htm
  • Bentlly
    Bentlly Posts: 12
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    Sorry if these were already answered...

    Q1) are VO2 max and calories burned directly proportional or inversely related? I.e. to ensure an underestimated calories burned calculation, should I try to estimate my VO2 max higher or lower than actual?

    Background:
    I am using a Polar HRM primarily for calculating calories (sorry :p) during bicycle rides, for use with MFP for weight loss. Of course I am interested in fitness, but my level of activity affects what I get to eat, and vice versa. If I ride for hard for 2 hours, I definitely need to eat back some of those calories. If I eat too much, I'm gonna have to ride further that evening.

    Later I will try to figure out VO2 max with some fitness test but for now, I want to estimate it so as to err on the side of underestimating the calories I burn because I am going to eat them back. The Polar HRM set my VO2 max at 42 while the software had me at 50. I looked at a chart in the help that said avg to low level of fitness should be around 35 for my age, weight etc. should I guess lower or higher to ensure underestimation of calories burned?

    Q2) what about basal metabolic rate? If polar estimates calories burned, it doesn't subtract the calories that would have been burned at rest, right? So eating back all of those calories would be a bad deal right?

    If I am going to eat back calories from exercise, do I need to subtract BMR calories for that period?

    You can see what I am getting at right? I want to be able to eat more if I exercise more, but I certainly don't want to eat more extra calories than I burned by exercising. I am sure that this is a very common concern

    Yes, I understand it's a rough estimate. Yes, I understand that counting calories I eat is also an estimate. But I spend a great deal of effort to regulate it.

    The best suggestion I have seen so far is to eat back half the calories. I prefer to calculate calories burned as accurate as possible, above BMR burn, and err to the lower side.

    More background: 45 years old, male, 6'2", 215#. Lost about 30# in 3 months counting calories with MFP, eating better and riding bicycle. Exercise is bicycling exclusively, bad leg prevents walking/jogging.

    Exercise consists of daily ride up a hill for 30 minutes, weekend road cycling and mountain biking. I ride hard, definitely anaerobic, high HR zones, but I like to think the consistency lends itself to accurate calorie calculations (compared to strength, HIIT, etc)

    Thanks!
  • heybales
    heybales Posts: 18,842 Member
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    Sorry if these were already answered...

    Q1) are VO2 max and calories burned directly proportional or inversely related? I.e. to ensure an underestimated calories burned calculation, should I try to estimate my VO2 max higher or lower than actual?

    Background:
    I am using a Polar HRM primarily for calculating calories (sorry :p) during bicycle rides, for use with MFP for weight loss. Of course I am interested in fitness, but my level of activity affects what I get to eat, and vice versa. If I ride for hard for 2 hours, I definitely need to eat back some of those calories. If I eat too much, I'm gonna have to ride further that evening.

    Later I will try to figure out VO2 max with some fitness test but for now, I want to estimate it so as to err on the side of underestimating the calories I burn because I am going to eat them back. The Polar HRM set my VO2 max at 42 while the software had me at 50. I looked at a chart in the help that said avg to low level of fitness should be around 35 for my age, weight etc. should I guess lower or higher to ensure underestimation of calories burned?

    Q2) what about basal metabolic rate? If polar estimates calories burned, it doesn't subtract the calories that would have been burned at rest, right? So eating back all of those calories would be a bad deal right?

    If I am going to eat back calories from exercise, do I need to subtract BMR calories for that period?

    You can see what I am getting at right? I want to be able to eat more if I exercise more, but I certainly don't want to eat more extra calories than I burned by exercising. I am sure that this is a very common concern

    Yes, I understand it's a rough estimate. Yes, I understand that counting calories I eat is also an estimate. But I spend a great deal of effort to regulate it.

    The best suggestion I have seen so far is to eat back half the calories. I prefer to calculate calories burned as accurate as possible, above BMR burn, and err to the lower side.

    More background: 45 years old, male, 6'2", 215#. Lost about 30# in 3 months counting calories with MFP, eating better and riding bicycle. Exercise is bicycling exclusively, bad leg prevents walking/jogging.

    Exercise consists of daily ride up a hill for 30 minutes, weekend road cycling and mountain biking. I ride hard, definitely anaerobic, high HR zones, but I like to think the consistency lends itself to accurate calorie calculations (compared to strength, HIIT, etc)

    Thanks!

    Q1 - Directly at the same HR. ie say HR was kept at 140 for a workout of 60 min for 150 lb male 40 yrs old. (gender, age, weight don't really matter, just showing constant)
    VO2max of 35 - 643 calories
    VO2max of 45 - 700 calories

    Don't try to play on the safe side too much if you exercise at decent levels for decent time - you could introduce much more deficit than you want, and won't get nearly the benefit from the exercise as you could.
    And since it's the deficit to the diet that creates weight loss, even without exercise, don't short your body what you are asking it to do.
    Especially doing higher aerobic/anaerobic high carb burning stuff with no strength training it sounds like - perfect recipe for burning off muscle mass if you aren't replenishing carbs enough.

    If that was a Polar HRM self-test for VO2max - accept what it finds. The study formula they use (BMI, resting HR, your selection of athletic level) started underestimating VO2max as you went over 45, getting worse the higher you went. So I'm betting your current 42 is already underestimated.
    Also, each time you lower weight, you need to redo the test, morning after rest day. Their FAQ's spell that out.
    Since VO2max is mL per KG per min - merely lowering your weight increased your VO2max, with no improvement to fitness by itself. But likely you have also.

    Q2 - Very true - no database table or HRM is going to know what you burned on top of what you might have been doing, whether that be sleep or resting or standing, ect.
    So actually you would not take out the BMR, you would take out more.

    Because MFP already has calculated, and you are eating to, an already accounted for calories burned per day - your maintenance. Divide by 1440, and that's how many calories you are expected to burn every minute already.

    You actually need to subtract that from what your HRM reports, to see how much you burned above and beyond what was already accounted for.

    You might like the HRM tab in this spreadsheet for the VO2max formula they have tweaked, and comparing calorie burn for you.
    Plus the MFP Tweak tab does what I describe above at the bottom, removes the already account for calories, plus actually a deficit if doing a % method.

    http://www.myfitnesspal.com/topics/show/813720-spreadsheet-bmr-tdee-deficit-macro-calcs-hrm-zones
  • viglet
    viglet Posts: 299 Member
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    :(

    I am honestly so confused... I feel like losing weight and becoming lean is such a science that I do not understand!

    In summary:
    I need to take the step test.. then adjust my polarf4t to the results of the step test and then my calories burnt will be more accurate?
  • heybales
    heybales Posts: 18,842 Member
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    :(

    I am honestly so confused... I feel like losing weight and becoming lean is such a science that I do not understand!

    In summary:
    I need to take the step test.. then adjust my polarf4t to the results of the step test and then my calories burnt will be more accurate?

    You can't adjust your FT4 to be more accurate, just can only test to see how far off it is.
    I haven't discovered what study Polar is using to estimate VO2max from only your BMI. If I could, height could be adjusted to correct it.

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

    If reasonable diets and exercise were done from that start, much of this would be unneeded.

    For instance, if you had been maintaining weight, best bet would be to find an exercise you could do to burn 250 calories on average daily, and then find 250 calories in your current diet you could leave out. No massive changes.

    Then as you lose weight, keep leaving some food out.
  • lucan07
    lucan07 Posts: 509
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    My old cheap Polar FT1 has no such problem I know my VO2max and use the Avg HR to calculate exercise calories myself which I then convert to Nett calories.

    Regardless the accuracy for weight loss it should not be a problem, if its consistent you will soon work out if its working for you or not and you can adjust results accordingly, even expensive HRM's are not going to be accurate for everyone!

    Its a tool to measure, the results need to be consistent and the output like anything computerised relies on the data input Rubbish in = Rubbish out.
  • mhotch
    mhotch Posts: 901 Member
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    Bump
  • heybales
    heybales Posts: 18,842 Member
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    My old cheap Polar FT1 has no such problem I know my VO2max and use the Avg HR to calculate exercise calories myself which I then convert to Nett calories.

    Regardless the accuracy for weight loss it should not be a problem, if its consistent you will soon work out if its working for you or not and you can adjust results accordingly, even expensive HRM's are not going to be accurate for everyone!

    Its a tool to measure, the results need to be consistent and the output like anything computerised relies on the data input Rubbish in = Rubbish out.

    So true, let it get you in to a better reasonable deficit range, and then adjust as needed.
  • rileysowner
    rileysowner Posts: 8,239 Member
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    Bump
  • nytrifisoul
    nytrifisoul Posts: 500 Member
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    I have a Suunto t3c but for all you polar owners....why not just log the bpm activity, or the average bpm and use an online hrm bpm calculator? Ive found that my Suunto calorie burn calculator is pretty close to some of them.
  • meeper123
    meeper123 Posts: 3,347 Member
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    Interesting
  • Tanya949
    Tanya949 Posts: 606 Member
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    Bump

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