HRM How accurate are they really???

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applekoko19
applekoko19 Posts: 85 Member
in Fitness and Exercise
Have I got this right???

When you wear your HRM {polar T4} it automatically calculates calories burned based on your (sex & weight & height) + (extra from physical exertion) = total calories burned.

So it uses this info to add in the calories your body would have burned had you done nothing??If I add 300calories from my run to my exercise log... am I adding calories onto my MFP 1200 limit that are really already included in my limit?? Am I giving myself an extra 300calories when i reality i only 'earned' a percentage of that number??

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  • rjo921
    rjo921 Posts: 130
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    from what I understand.....if you burn 300 calories...then you can add 300 more calories to your 1200 calories that you are alloted during the day....so you have to head up to 1500. That is what I understand....:smile:
  • heybales
    heybales Posts: 18,842 Member
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    Have I got this right???

    When you wear your HRM {polar T4} it automatically calculates calories burned based on your (sex & weight & height) + (extra from physical exertion) = total calories burned.

    So it uses this info to add in the calories your body would have burned had you done nothing??If I add 300calories from my run to my exercise log... am I adding calories onto my MFP 1200 limit that are really already included in my limit?? Am I giving myself an extra 300calories when i reality i only 'earned' a percentage of that number??

    Notice the info they have allows them to do the exact same BMR calc as MFP and other sites that do BMR calc - so they leave the BMR burn out of that time period.

    They also base the total burn on you actually having the BMR that is estimated. But sadly, if you have slowed your BMR down by underfeeding, that burn is actually less.

    As to general accuracy, here is the study. Not surprising women are potentially more incorrect - because women are tougher and more willing to eat too little and lower BMR! Men are generally wimps, but more correct with default calcs.

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

    To correct one of the figures at least.

    http://www.myfitnesspal.com/topics/show/466973-i-want-to-test-for-my-max-heart-rate-vo2-max
  • SteveHunt113
    SteveHunt113 Posts: 648 Member
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    I've wondered the same thing regarding the base calories that are already calculated for a given time that you add exercise to. I purchased a BodyMedia fit to see what it says my calorie burn is throughout the day. I see that when I'm doing nothing, like sleeping, it has my burn at about 1.5 calories every 2 minutes. So, if I were to workout for 30 minutes, it would come to 22.5 calories over. When you look at it like that, it's not a real big deal.

    In the end, all of these devices are make their best guess about how many calories you are burning. Only time logging calories and watching your weight will you know if you are doing it right, or if adjustments are needed.
  • heybales
    heybales Posts: 18,842 Member
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    from what I understand.....if you burn 300 calories...then you can add 300 more calories to your 1200 calories that you are alloted during the day....so you have to head up to 1500. That is what I understand....:smile:

    That's correct, because your 1200 already includes a deficit, exercise added later and not fed could make it a very unsafe deficit.
  • applekoko19
    applekoko19 Posts: 85 Member
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    Haybales.... ""Notice the info they have allows them to do the exact same BMR calc as MFP and other sites that do BMR calc - so they leave the BMR burn out of that time period."" Do they really do this subtraction?? If they do then wonderful, if not then I just want to know... out of curiosity. I know it will not be a huge difference but so many people talk about eating back exercise calories with almost religious zeal on MFP that you feel guilty when you don't!
  • Hawksbillus
    Hawksbillus Posts: 128 Member
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    If you've listed yourself as "sedentary" then anything you do above and beyond sitting on the couch counts as additional calories burned that you can then eat back (if you like).

    But, if you want to get really technical, that 300 calories was not in addition to the calories your body burns by doing nothing. Your body burns calories just by being alive. You can calculate this number (your BMR or Basal Metabolic Rate) at sites like this: http://www.bmi-calculator.net/bmr-calculator

    Here's another experiment you can do. Put on your HRM and sit on the couch watching TV. After a few minutes of resting, turn on your HRM and let it run for 10 minutes and calculate how many calories you burn just sitting on the couch. Then multiply that number by 6 for how many calories you'd burn in an hour and then take THAT number and multiply it by 24 to see how many you burn in a day. I did this the other day with my new HRM and the total number per day was almost exactly the same as my BMR calculated from the link above.

    So, if you really, really, really want to be accurate you would do this: for every hour you work out you would take the calories burned that your HRM gives you and subtract from that the number of calories you calculate you burn in an hour at rest and then take that final number and plug it into MFP.

    But, that's a real hassle. Besides, the exercise you do during a workout has benefits that continue after you turn off your HRM, because your heart takes a while to go back to its resting rate and whatnot. Most people just log the number their HRM tells them to log and most people lose weight this way, so, it's probably a wash and doesn't make that much of a difference.
  • applekoko19
    applekoko19 Posts: 85 Member
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    If you've listed yourself as "sedentary" then anything you do above and beyond sitting on the couch counts as additional calories burned that you can then eat back (if you like).

    But, if you want to get really technical, that 300 calories was not in addition to the calories your body burns by doing nothing. Your body burns calories just by being alive. You can calculate this number (your BMR or Basal Metabolic Rate) at sites like this: http://www.bmi-calculator.net/bmr-calculator

    Here's another experiment you can do. Put on your HRM and sit on the couch watching TV. After a few minutes of resting, turn on your HRM and let it run for 10 minutes and calculate how many calories you burn just sitting on the couch. Then multiply that number by 6 for how many calories you'd burn in an hour and then take THAT number and multiply it by 24 to see how many you burn in a day. I did this the other day with my new HRM and the total number per day was almost exactly the same as my BMR calculated from the link above.

    So, if you really, really, really want to be accurate you would do this: for every hour you work out you would take the calories burned that your HRM gives you and subtract from that the number of calories you calculate you burn in an hour at rest and then take that final number and plug it into MFP.

    But, that's a real hassle. Besides, the exercise you do during a workout has benefits that continue after you turn off your HRM, because your heart takes a while to go back to its resting rate and whatnot. Most people just log the number their HRM tells them to log and most people lose weight this way, so, it's probably a wash and doesn't make that much of a difference.

    I actually contemplated doing the relaxing and multiplying bit with the HRM to get a BMR figure but never bothered! Also I have had my activity level at sedentary since I started on here back in November and I just didn't think of it again but now I am fairly active so maybe I need to change that! I just get fixated on numbers so the HRM question was really annoying me.
  • heybales
    heybales Posts: 18,842 Member
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    Haybales.... ""Notice the info they have allows them to do the exact same BMR calc as MFP and other sites that do BMR calc - so they leave the BMR burn out of that time period."" Do they really do this subtraction?? If they do then wonderful, if not then I just want to know... out of curiosity. I know it will not be a huge difference but so many people talk about eating back exercise calories with almost religious zeal on MFP that you feel guilty when you don't!

    I've compared Polar estimates to this other study's formula estimates, since I know my VO2max.
    The difference is about my BMR for that time, which the study formula doesn't know from estimate.

    http://www.braydenwm.com/calburn.htm
  • heybales
    heybales Posts: 18,842 Member
    Options
    If you've listed yourself as "sedentary" then anything you do above and beyond sitting on the couch counts as additional calories burned that you can then eat back (if you like).

    But, if you want to get really technical, that 300 calories was not in addition to the calories your body burns by doing nothing. Your body burns calories just by being alive. You can calculate this number (your BMR or Basal Metabolic Rate) at sites like this: http://www.bmi-calculator.net/bmr-calculator

    Here's another experiment you can do. Put on your HRM and sit on the couch watching TV. After a few minutes of resting, turn on your HRM and let it run for 10 minutes and calculate how many calories you burn just sitting on the couch. Then multiply that number by 6 for how many calories you'd burn in an hour and then take THAT number and multiply it by 24 to see how many you burn in a day. I did this the other day with my new HRM and the total number per day was almost exactly the same as my BMR calculated from the link above.

    So, if you really, really, really want to be accurate you would do this: for every hour you work out you would take the calories burned that your HRM gives you and subtract from that the number of calories you calculate you burn in an hour at rest and then take that final number and plug it into MFP.

    But, that's a real hassle. Besides, the exercise you do during a workout has benefits that continue after you turn off your HRM, because your heart takes a while to go back to its resting rate and whatnot. Most people just log the number their HRM tells them to log and most people lose weight this way, so, it's probably a wash and doesn't make that much of a difference.

    I actually contemplated doing the relaxing and multiplying bit with the HRM to get a BMR figure but never bothered! Also I have had my activity level at sedentary since I started on here back in November and I just didn't think of it again but now I am fairly active so maybe I need to change that! I just get fixated on numbers so the HRM question was really annoying me.

    As that study page I linked to shows, HRM estimates of calorie burn are only possibly accurate within an aerobic zone, outside that forget.

    So forget wearing the HRM all day. Only for aerobic exercise.
  • meshashesha2012
    meshashesha2012 Posts: 8,326 Member
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    i wouldnt necessarily immediately eat back those calories though mainly because how many of those calories you burned are ones that are already accounted for in your daily burn.

    for instance if you average 100 calories an hour for just sitting on the couch and then you do an exercise that burns 300, you really only burned 200 additional calories.

    plus like the previous poster said, i think the calories burned are kind of iffy depending on the type of exercise. for instance i can get the same heart rate when i'm on the versaclimber as i can when running, running or lifting a heavy weight. even though the heart rates are the same, each one feels different. the weight seems harder (i can't talk), then running, then the versaclimber.. it's possible that i'm truly burning the same amount of calories doing all 3, but i dunno
  • heybales
    heybales Posts: 18,842 Member
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    plus like the previous poster said, i think the calories burned are kind of iffy depending on the type of exercise. for instance i can get the same heart rate when i'm on the versaclimber as i can when running, running or lifting a heavy weight. even though the heart rates are the same, each one feels different. the weight seems harder (i can't talk), then running, then the versaclimber.. it's possible that i'm truly burning the same amount of calories doing all 3, but i dunno

    Anaerobic compared to aerobic would be the difference. Probably are the same burn for the 2 aerobic running and climber.

    And the HRM's while showing you your HR during lifting, will be incorrect for calorie burn related to anything anaerobic. The formula's are just for aerobic type activities between 90-150 bpm.
    And while your HR may not go into the anaerobic cardio zone (say HR is above 170 and your cardio is anaerobic) while weight lifting, it is the same anaerobic activity without fat as energy, totally ATP and glucose recovery, and the recovery is not aerobic either.

    You can get an estimate based on elevated HR, but it will be overstated for weight lifting. Actually, for sprint intervals too.

    Comments and study on this page that shows why the above is the case.
    http://www.braydenwm.com/calburn.htm
  • meshashesha2012
    meshashesha2012 Posts: 8,326 Member
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    plus like the previous poster said, i think the calories burned are kind of iffy depending on the type of exercise. for instance i can get the same heart rate when i'm on the versaclimber as i can when running, running or lifting a heavy weight. even though the heart rates are the same, each one feels different. the weight seems harder (i can't talk), then running, then the versaclimber.. it's possible that i'm truly burning the same amount of calories doing all 3, but i dunno

    Anaerobic compared to aerobic would be the difference. Probably are the same burn for the 2 aerobic running and climber.

    And the HRM's while showing you your HR during lifting, will be incorrect for calorie burn related to anything anaerobic. The formula's are just for aerobic type activities between 90-150 bpm.
    And while your HR may not go into the anaerobic cardio zone (say HR is above 170 and your cardio is anaerobic) while weight lifting, it is the same anaerobic activity without fat as energy, totally ATP and glucose recovery, and the recovery is not aerobic either.

    You can get an estimate based on elevated HR, but it will be overstated for weight lifting. Actually, for sprint intervals too.

    Comments and study on this page that shows why the above is the case.
    http://www.braydenwm.com/calburn.htm

    so i wear my HRM every time i work out and i do a lot of HIIT workouts. so basically would my end calorie result be an overestimation or underestimation?

    i dont eat my exercise calories back so it's not that big of a deal, but i think it's going to be something to keep in mind for once i get to my goal weight


    thanks for the link. i'll go read that now
  • heybales
    heybales Posts: 18,842 Member
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    so i wear my HRM every time i work out and i do a lot of HIIT workouts. so basically would my end calorie result be an overestimation or underestimation?

    i dont eat my exercise calories back so it's not that big of a deal, but i think it's going to be something to keep in mind for once i get to my goal weight

    So during the activity - over estimated.
    Recovery from the activity - probably over what was estimated during.

    That's the great thing about sprint intervals and weight lifting, while calorie burn during the activity isn't that great, the body's recovery afterwards uses much more energy. That's why eating that back works so great, only eating back the carb usage part that needs recovery, the fat burning part later - forget it.

    Compared to cardio is mostly during the activity, very little afterwards.

    The kicker here is - there must be recovery time. If there is not, then that doesn't happen, you don't get stronger. If you don't get stronger and not enough rest, the efforts actually start being less intense.

    I finally did a treadmill push up to 9mph for a minute, and only got up to lactate threshold. Much better improvement.
    But my last sprint intervals on the track were about 10mph for the 1 min/1min efforts, and 12 mph for the 15 sec/45 sec efforts.

    So on the treadmill, HR up to 171 was still aerobic - barely.
    On the track, 171 seen on the way up and down was anaerobic. Walking recovery is aerobic though.

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