Calories Not Accurate on HRM?

24

Replies

  • jazzmensa
    jazzmensa Posts: 9
    I picked up a cheap one in Lidl yesterday (£14.99) and have worn it with chest strap for 24 hrs during which time I have deliberately not exercised. It tells me I have burnt off 3054 calories just doing day-to-day activities; this seems a little excessive to say the least! Obviously I am overweight but if I was genuinely using that many surely I wouldn't have to cut down on food! I was happy that the pulse rate was correct - the lowest was 49 at rest and I hit 120 running up the stairs.
  • ohohraptor
    ohohraptor Posts: 205 Member
    Hmm.. Should I not wear it tomorrow to yoga then?
  • anubis609
    anubis609 Posts: 3,966 Member
    Hmm.. Unless your HR rapidly fluctuates between the Fitness zone and resting or the Fat Burn zone, it would seem that your HRM might be off. I have a Polar FT7, and when I first got it, I tested it against other measures as far as accuracy for measuring HR is concerned. First, manually checking my HR, then again with my bp machine... both were spot on as far as HR consistency. 451 calories burned in 50 minutes of core/strength training does seem a bit of a stretch. Maybe you got the transmitter wet? I usually just take water from my fingers and run it along the sensor pads and the area of skin that it touches. I don't soak it. You could try that. If it still seems like it's malfunctioning, contact Polar. They may be able to troubleshoot it.
  • ohohraptor
    ohohraptor Posts: 205 Member
    HRMs are NOT meant to be used for activities like weight-lifting. They're only designed to be accurate for constant cardio activity like walking/running/etc. And not for "casual" activity like walking around the store or things like that. (They're not designed to be worn all day.)

    There was a great post awhile back by Azdak, I think, about why you can't use HRM's for strength training calories burned, but I don't have it bookmarked...

    Really? I had no idea! I thought it worked for everything. Why is it not meant for strength training?

    Found it - here's the original post I was thinking of - though I do recommend you read that other one, too. http://www.myfitnesspal.com/blog/Azdak/view/hrms-cannot-count-calories-during-strength-training-17698

    This is from the first article:
    4. HRMs can be used to accurately count calories expended during strength training and during rest and 24-hour activity periods.

    ????
  • Mindful_Trent
    Mindful_Trent Posts: 3,954 Member
    Hmm.. Should I not wear it tomorrow to yoga then?

    I wouldn't. In most yoga classes (as far as I know) you are not in a constant-aerobic-state of activity. It's more stretching and using your body weight for strengthening. It's not the type of activity that HRM's are really designed for.
  • TrainingWithTonya
    TrainingWithTonya Posts: 1,741 Member
    Have you had any caffeine today? What about medications for allergies, asthma, etc.? Those will all increase heart rate in addition to exercise which will increase the calorie burn calculated.

    Another thing to consider is that MFP's strength training MET level is for general exercise by people who are lifting light to moderate weights with rest between sets where the heart rate has a chance to go back down. If you are lifting heavy and/or not giving yourself adequate rest between sets, you will have an elevated heart rate through more of the exercise which will give you a higher calorie burn.



    I purposely didn't have coffee this morning because I wanted to see how accurate the monitor was. I don't give myself a lot of time between sets, although I don't lift heavy by far. I'm pretty weak still. :/

    Yeah, it read your heart rate as elevated the whole time you were working out, but while you are lifting weights you have highs and lows in your heart rate instead of being at steady state like you would for cardio. Since you didn't rest for 2-5 minutes between sets, the HRM didn't see the lows because your heart rate didn't come down as much during your brief rest. Just because the heart rate is beating that high doesn't mean your body is actually burning more, though. You burn a little bit more from your heart working harder, but not nearly as much as you burn while you are actually working the other muscles. I'd go with MFP on the strength work and the HRM on the cardio where you achieve a steady state.
  • polar5554
    polar5554 Posts: 576 Member
    Ha...I am in the opposite situation that you are in.

    I too just got the FT4 and my first day using it was this morning and mine gave me a reading of only 223 calories burned for 40 minutes of P90...

    Just out of curiosity...you DID get the female version correct?
  • Mindful_Trent
    Mindful_Trent Posts: 3,954 Member
    HRMs are NOT meant to be used for activities like weight-lifting. They're only designed to be accurate for constant cardio activity like walking/running/etc. And not for "casual" activity like walking around the store or things like that. (They're not designed to be worn all day.)

    There was a great post awhile back by Azdak, I think, about why you can't use HRM's for strength training calories burned, but I don't have it bookmarked...

    Really? I had no idea! I thought it worked for everything. Why is it not meant for strength training?

    Found it - here's the original post I was thinking of - though I do recommend you read that other one, too. http://www.myfitnesspal.com/blog/Azdak/view/hrms-cannot-count-calories-during-strength-training-17698

    This is from the first article:
    4. HRMs can be used to accurately count calories expended during strength training and during rest and 24-hour activity periods.

    ????

    If you continue reading - he states that all of those "facts" are myths and untrue.
  • mickeymousedl
    mickeymousedl Posts: 17
    I've found that the machines under or over estimate my calories. The HRM is based on your weight height sex and age. The machines have a general heght and sex. I always go with my HRM totals over the machines at the gym.

    I had a Polar F6 and I just bought the Polar FT7
  • ohohraptor
    ohohraptor Posts: 205 Member
    Have you had any caffeine today? What about medications for allergies, asthma, etc.? Those will all increase heart rate in addition to exercise which will increase the calorie burn calculated.

    Another thing to consider is that MFP's strength training MET level is for general exercise by people who are lifting light to moderate weights with rest between sets where the heart rate has a chance to go back down. If you are lifting heavy and/or not giving yourself adequate rest between sets, you will have an elevated heart rate through more of the exercise which will give you a higher calorie burn.



    I purposely didn't have coffee this morning because I wanted to see how accurate the monitor was. I don't give myself a lot of time between sets, although I don't lift heavy by far. I'm pretty weak still. :/

    Yeah, it read your heart rate as elevated the whole time you were working out, but while you are lifting weights you have highs and lows in your heart rate instead of being at steady state like you would for cardio. Since you didn't rest for 2-5 minutes between sets, the HRM didn't see the lows because your heart rate didn't come down as much during your brief rest. Just because the heart rate is beating that high doesn't mean your body is actually burning more, though. You burn a little bit more from your heart working harder, but not nearly as much as you burn while you are actually working the other muscles. I'd go with MFP on the strength work and the HRM on the cardio where you achieve a steady state.

    Will do. Tomorrow I have a run so we'll see what happens then. I just tried it again and after taking my heart rate manually it was exactly correct. I hope my sports bra being over it wasn't messing it up... Or maybe it was too wet.
  • waverly9876
    waverly9876 Posts: 605 Member
    bump
    Im confused after reading that article. Whats the point of buying a heart rate monitor then?
  • ohohraptor
    ohohraptor Posts: 205 Member
    Ha...I am in the opposite situation that you are in.

    I too just got the FT4 and my first day using it was this morning and mine gave me a reading of only 223 calories burned for 40 minutes of P90...

    Just out of curiosity...you DID get the female version correct?

    Yep, definitely got a the female one!
  • ohohraptor
    ohohraptor Posts: 205 Member

    If you continue reading - he states that all of those "facts" are myths and untrue.

    Oh. :o Guess I should probably finish the article before I start blabbing. :)
  • Mindful_Trent
    Mindful_Trent Posts: 3,954 Member
    bump
    Im confused after reading that article. Whats the point of buying a heart rate monitor then?

    The end of the 2nd article I posted sums it up well:
    Does this mean that heart rate monitors are not useful? Not at all. For a number of aerobic activities--most ellipticals, spin classes, running outdoors, other aerobic-style classes--they are still the best option for estimating calories. And they can be used for circuit training and some mixed classes or cross fit workouts--both as a more vague estimate of calories burned, but also for workout-to-workout comparisons. And for many people, by the time you get to the point where you can and need to start doing more intense lifting and circuit workouts (e.g. tabata, crossfit), calories burned during a workout is less relevant anyhow.
  • mikeyml
    mikeyml Posts: 568 Member
    I was in a similar situation to you when I first bought my HRM. I had been using a HRM that came with my treadmill but it was only good for reading my HR and not for estimating calories. My treadmill would estimate the calories burned and that's what I used when entering exercise in here. Since the weather is getting nicer and I want to exercise outside more, I went out and bought a Polar FT7. The first time I wore it, it said I burned 100 more calories from my normal treadmill workout than the treadmill estimated. I was skeptical, but the HR frequency was nearly the exact same as when I used the treadmill's HRM. I asked a lot of people on and off MFP, including some personal trainers, which one is more accurate and the answer was resoundingly the Polar HRM. So that's my take on it.

    Now as far as using it during strength training, I don't know if I would use it for that. I try to use mine solely for cardio or really intense activity. There is just too much resting in strength training in my opinion to use a HRM. Likewise I would not wear it for 24 hours to get an estimate of daily calories burned.
  • THISisTARRAN
    THISisTARRAN Posts: 487 Member
    I am no expert, but I am wondering if you used tap water? Mine HRM specifically says DO not use tap water to get the strap wet. I'm not sure why. I think it said to use spit or they sell specific water made for it. Could that be it?
  • leomom72
    leomom72 Posts: 1,797 Member
    i have the ft4, and i trust it more than mfp..it is a sensor from your heart rate, so should be very accurate. you are supposed to get the tab things wet on the back before each use though, i'm sure you knew that :) there were so many responses, i didn't read thru them all, but i'm sure you will find what you are looking for..best of luck :)
  • arodriguez24
    arodriguez24 Posts: 81 Member
    I agree with the resting in strength training but if you doing some circuit strength training then it would be very useful, and I believe that the FT series in polar is designed to also consider strength training activities. For instance if I'm doing curls for 20 minutes with little movement I only burn a little, but if I'm switching back and forth from different exercises and out of breath after a series I see that I burned more, I know its not 100% accurate but its better than nothing.
  • RatBoyGL
    RatBoyGL Posts: 100
    I picked up a cheap one in Lidl yesterday (£14.99) and have worn it with chest strap for 24 hrs during which time I have deliberately not exercised. It tells me I have burnt off 3054 calories just doing day-to-day activities; this seems a little excessive to say the least! Obviously I am overweight but if I was genuinely using that many surely I wouldn't have to cut down on food! I was happy that the pulse rate was correct - the lowest was 49 at rest and I hit 120 running up the stairs.

    Actually, that MAY not be that excessive.

    I am 6'2, 201, and I burn approximately 1904 calories a day at rest.

    Your brain burns more calories in a day than you can ever hope to burn at a gym. Trust me on that one. It burns calories to keep your lungs pumping, your heart pumping, sending the electronic signals to all your muscle groups, moving your mouth while eating, blinking your eyes, you name it.

    The rate at which you burn in a day at full rest is called BMR.

    MFP sets your goal cals to BMR minus a certain number (your deficit) in order to make you lose weight.
  • robertf57
    robertf57 Posts: 560 Member
    WOW. Remember the HRM is just a tool for estimating caloric expenditures. The are only as reliable as the estimation method and equations they incorporate a.d generally are not suitable for estimating anything other than steady state aerobic activity. Quite frankly, I find their greatest value is keeping me honest: I have an objective measure of how hard I am working during my workout based on my HR over the exercise period.

    Unless you are going to actually measure the consumption of oxygen directly and or CO2 production with fairly expensive medical equipment. All the calorie estimates are just that, estimates!
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