Question About Polar HRM Accuracy (High reading)

slmckenzie
slmckenzie Posts: 22 Member
edited September 25 in Fitness and Exercise
So, I put my Polar Ft4 to the test tonight, when my wife and I went to the gym for the first time. I'm sitting here right now, afraid to go to bed, because I'm scared I'm not going to be able to move in the morning!

Anyway, I wore my HRM the entire time I was there, from starting out doing cardio, to ending doing strength training. I ended up having the HRM run for about 87 minutes. During that time, about 55 or so minutes of it was just spent on cardio. Of that time,

Stationary Bike: 20 minutes, 7.2 miles
Treadmill: 25 minutes, 1.65 miles
Stairmaster (omg!): 5 minutes, 0.28 miles

From that point, I moved on to strength training. However, almost the entire time, my heart rate was quite high. I think most of the exercise it was about 165-185. According to the watch, it says that I was "In Zone" during that time for 73 total minutes. It said that my average heart rate was 150, with my maximum being 183. I guess that's almost at the top of where the cardio heart rate should be?

Anyway, I guess my main question is that my HRM is telling me that for the 87 minute session, I burned 1,171 calories! Now, I know people said to get the Polar over the Timex, which was known to way over calculate calories burned. But it almost seems that 1,171 calories is exceedingly high! Granted, I was drenched in sweat, I'd never really done anything like tonight for at least the past 6 or 7 years, and I was trying to work my butt off.

So, is that calorie burn correct? Is it due to the fact that my heart rate was so much higher during the entire session? If so, that's great, and I'll take it, but it means that I need to eat more, because it puts me at a net of about 400 calories for the entire day!

So, yeah. Does this seem reasonable? As you can tell from my signature, I'm 5'6", 25, and 210 lbs.

Thanks!

Replies

  • AmandaB4588
    AmandaB4588 Posts: 655
    I'm curious to see what people say, as I just had a 1095 calorie burn playing racquetball. I have trusted my Polar HRM up to this point but it's crazy to see your calories burned in the thousands!
  • jenrogerspm
    jenrogerspm Posts: 21
    If you want an accurate calorie count you need to actually do the "math" If you go online you can find the equation for calories burned based on your body weight and resting heart rate. 87 minutes is a long time for a workout so your calorie count should be at least in the high 800's.
  • MsLisaB
    MsLisaB Posts: 256
    Hi there,

    I went to this website http://www.triathlontrainingblog.com/calculators/calories-burned-calculator-based-on-average-heart-rate/ put your stats in the calculator and got 1,146 calories burned, so I'd say your polar is spot on.

    That's a great workout by the way. I hope you're not too sore over the next couple of days. :smile:
  • mamagooskie
    mamagooskie Posts: 2,964 Member
    I can burn 1000 calories in about 1 hour 40 min........so based on what you say your weight is I would say that sounds about right!
  • AmandaB4588
    AmandaB4588 Posts: 655
    Hi there,

    I went to this website http://www.triathlontrainingblog.com/calculators/calories-burned-calculator-based-on-average-heart-rate/ put your stats in the calculator and got 1,146 calories burned, so I'd say your polar is spot on.

    That's a great workout by the way. I hope you're not too sore over the next couple of days. :smile:

    Thanks for sharing this website! It looks like my HRM is spot on as well. What a relief!
  • slmckenzie
    slmckenzie Posts: 22 Member
    Great! Thanks all for the quick help! I'm moving MFP more and more :)

    So I guess a somewhat relative question to this would be, does the 1200 calories to eat minimum per day include any subtractions from cardio exercise, or is it a standalone value? I guess what I'm trying to ask is if I eat, say 1600 calories, but then have an intense workout and burn 1,000 calories, leaving me with a net total for the day of 400 calories, is that ok? Or does the total of food - (minus) exercise need to be greater than 1200? I'm just wondering, since it's after 11pm here, and I'm only at about a net 500 or so calories for the day!
  • kcphilly
    kcphilly Posts: 71
    The first time I used my HRM, also a Polar F4, I did around 90 minutes also at the gym and was pretty shocked to see it said I burned 700 calories (way over what the gym machines calculate) I tested it aganist 3 websites that calculate calories burned and they all confirmed what the HRM said. I know it seems like a crazy amount but it seems accurate!

    Edit to add: about the net calories...yes your goal should be to get around 1,200 Net. I wouldn't worry too much about today, just for the future now you can plan ahead on days you know you're going to the gym to work out for about that long/intense so you can get some extra calories in earlier in the day.
  • agdeierl
    agdeierl Posts: 378 Member
    I've heard that HRMs are not accurate for use during strength training. So that might be something to consider, unfortunately. I have a Polar as well, and personally, I just use it during cardio, and then I just don't bother with it during strength training and use MFP's estimates instead, which are still not super accurate, but from what I've learned, closer to accurate than what HRMs say.
  • healthyandthin
    healthyandthin Posts: 104 Member
    Hi there,

    I went to this website http://www.triathlontrainingblog.com/calculators/calories-burned-calculator-based-on-average-heart-rate/ put your stats in the calculator and got 1,146 calories burned, so I'd say your polar is spot on.

    That's a great workout by the way. I hope you're not too sore over the next couple of days. :smile:

    Thanks for sharing this website! It looks like my HRM is spot on as well. What a relief!

    Thank you for the link! It looks like my -elliptical machine- shows the right calorie number.
  • sirphilipe
    sirphilipe Posts: 43 Member
    You total calories for the day are just based on your diet. Any exercise is additional calories..

    Don't be worried every once in a while having a huge left over balance. But don't do it daily. I usually have about 200 calories left over for the day...

    BTW my Polar HRM just arrived at the post office today and I am taking it away with me out of town and the hotel we are staying at has it's own gym!

    Good luck and keep at it!
  • sirphilipe
    sirphilipe Posts: 43 Member
    I've heard that HRMs are not accurate for use during strength training. So that might be something to consider, unfortunately. I have a Polar as well, and personally, I just use it during cardio, and then I just don't bother with it during strength training and use MFP's estimates instead, which are still not super accurate, but from what I've learned, closer to accurate than what HRMs say.

    Why wouldn't they be accurate while you are doing weights. The calories burned is based on the rate your heart goes at....????
  • spaboleo
    spaboleo Posts: 172
    If you want an accurate calorie count you need to actually do the "math" If you go online you can find the equation for calories burned based on your body weight and resting heart rate. 87 minutes is a long time for a workout so your calorie count should be at least in the high 800's.

    No, that's wrong.
    That might even be more inaccurate than the polar HRM.
    Polar is the only one company, specialized on building HRMs and that since I can think...

    Most of the HRMs just take a standard-formula (most of them for light jogging) and estimate the burned calories by calculation. The formula (there are different ones) take age, gender, height, weight as static parameters and your heart rate and the duration as dynamic parameters.
    A cheap HRM that e.g. only asks for age and weight might be even more inaccurate than other ones.

    All these HRMs base their calculations on a effect that Prof. Concoi, an italian sports scientist, discovered. Between a heart rate of 110 and 165 bpm the burned calories and the heart rate correlate linear.
    That means...the higher your heart rate is the equally more calories you'll burn.


    The downside of using this formula is...it is only accurate if you really do sports (heart rate > 110) and that it gets quickly inaccurate if your heart rate climbs above 165.


    Why is polar better than others?
    The newer polar systems (e.g. the multisport Polar RS300x) has calculation algorithms that are based on research polar has done in that field.
    Besides age, gender, weight, ... they take into account how often you exercise and you can enter the lung volume (ascertained by a fitnesstest).
    The newer models even communicate with a GPS sensor, aswell as an gyroscope or a step-sensor clipped to your shoes.
    Via GPS your actual speed can be calculated and a gyroscope or step-sensor is able to detect how many steps you are doing. This allows the HRM to find out if you are running light (low speed, many steps) or hard (higher speed with lesser steps) or even biking (much faster than running and continous steps), which of course has influence on the required algorithm for calculation.
    The modern HRMs are, as far as I know, even capable to determine intensity-intervall and do split calculations, which leads to more accuracy!

    I think polar builds the most advanced HRMs, for that matter.

    And what else do we learn? It is important to set up the parameters (age, gender, WEIGHT!) correctly and always to the current ones :wink:


    @ slmckenzie:
    Because the used polar HRM is an beginner model I would see the burned calories with an accuracy of +/-100kcal.
    But what the HRM displayed correctly is the tendency of your burn!
    And it was massive, because you exercised really hard over a long time period.

    I attend a spinning class regularly and I usually burn up to 1500kcal in 90min. cycling. Usually at 75-85% of my max Heart Rate.
    So you might have burned around 900-1100kcal for sure :)

    Great! Thanks all for the quick help! I'm moving MFP more and more :)

    So I guess a somewhat relative question to this would be, does the 1200 calories to eat minimum per day include any subtractions from cardio exercise, or is it a standalone value? I guess what I'm trying to ask is if I eat, say 1600 calories, but then have an intense workout and burn 1,000 calories, leaving me with a net total for the day of 400 calories, is that ok? Or does the total of food - (minus) exercise need to be greater than 1200? I'm just wondering, since it's after 11pm here, and I'm only at about a net 500 or so calories for the day!

    Yes you have to eat back your burned calories.
    Because your body needs the energy.

    You have to see the calorie restriction of MFP as you only dietary approach!
    You exercise a) for fun, b) to gain muscles and get fitter and c) to be able to eat a little bit more :wink:

    Try to aim for matching your net-calorie goal daily, but don't be to metuculous. :wink:
  • agdeierl
    agdeierl Posts: 378 Member
    I don't perfectly understand the science of it (why they're not the best to use for strength training) myself, so I am going to quote a very knowledgeable and well-respected member of the MFP community, SHBoss1673 (previously known as Banks1850), and then you can do the research from there if you like:

    Basically he starts out by staying that there are two basic reasons why an HRM is not very accurate to calculate calories burned during strength training:

    "1) The HRM is a simple ecg device that measures the electrical impulses given off by the heart when it pumps. Knowing the approximate size and other stats of the individual, formulas can be used to predict the amount of oxygen being used, and if VO2 is used, an accurate depiction of calories burned can be garnered. Even without VO2, relatively accurate calorie counts can be achieved for most individuals (assuming you are in the "normal" range of humans with regards to % oxygen burned.
    When doing exercise routines that involve heavy, short bursts of energy, you place artiificial stress on those muscles, which raises blood pressure and increases heart rate but the resulting calorie burn from the activity is not in line with the increase in heart rate. Plus, since most HRM's take averages over 5 to 10 second intervals, depending on the speed of the specific exercise repetition, it may not even register a significant change.

    2) Weight training doesn't raise calorie burn the same way that cardio does. Since part of weight training is the microscopic tearing of muscle fibers, in order to rebuild them larger and stronger, calorie burn from the activity isn't necessarily indicative of the total rise in energy requirements for the duration of the muscle reparation activity. I.E. when you weight train, for anywhere from 8 to 48 hours after the activity, calorie burn will be in a slightly elevated state to compensate for the extra energy needed to repair and build new muscle tissue."
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