Accuracy of HRM????

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hmayo86
hmayo86 Posts: 81 Member
in Fitness and Exercise
I recently purchased a scosche rhythm HRM and I'm not sure how accurate it is. I got it because I like the idea of no chest strap (don't have to worry about getting it wet to make sure it's on, the rhythm just straps to your forearm). I realize, however, the chest straps may be more accurate. I've done 5 workouts with the rhythm. 2 days of Jackie Warner 40 minute Power Circuit (764 and 747 calories burned). 2 days of Jillian Michaels' Kickbox Fastfix (20 minutes- 363 and 453 calories burned). And one 20 minute Zumba for Kinect burned 354 calories. Does anyone know if these burns seem plausible? I'm a 26 y/o female weighing 242 lbs. I'm really hoping I didn't just waste $100!!!

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  • animatorswearbras
    animatorswearbras Posts: 1,001 Member
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    They do sound high but still plausible, I think I've heard people say before that even with the chest strap ones(I have an FT4), even though apparently more accurate, you still have to take them as a good guess. If I was you I'd log what it says but if you're eating back your cals maybe be a tad conservative like only eating 2/3's and see how that goes? That's just my opinion hopefully someone else may come along and give you a more educated response.
  • hmayo86
    hmayo86 Posts: 81 Member
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    I've been trying to stay a little under my daily calorie goal just in case the burn rate is off. Thanks for the input! :)
  • MinnieInMaine
    MinnieInMaine Posts: 6,400 Member
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    Those seem lke really high burns to me...usually anything higher than 12 calories per minute is likely an overestimate. Even when I was at 260 it was unlikely that I'd burn that much.

    I tried looking it up but there's not too much info on the website... Do you input personal info like height, weight, gender, etc into the app?
  • ROBJ3411
    ROBJ3411 Posts: 72 Member
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    HRM are all generally accurate if used properly, they tell you how hard your heart is working at a given point in time. Most HRM have an Average HR function that tells you the hearts work over time, those two functions are generally Very accurate....

    Now the tricky part is when you start using it to count calories, this information is only as accurate as the information you put in and how the HRM calculates calories. If you only put in your age, then the "computer" is taking some form of
    1. 220-Age to predict your max HR",
    2. your Resting HR
    3. a guess on your calories consumed based on your weight.

    to do the calculations on the calories burned. All of these can have some to alot of error in them.

    For instance my wife is 38 so 220- 38 gives her a MAX HR of 182. her real MAX HR is a 210, so there is alot of error there.

    IF your HRM allows you to put Resting or Min HR and your take the time to figure it out accurately ( easy to do), and you obtain your "true" Max HR (There are some easy ways to do it), you are left with the error based on Weight (which is much more difficult to eliminate unless you spend the money to get it tested.) This will gets you pretty close with calories. Just make sure to update your Weight and Resting HR over time as these will change.
  • omma_to_3
    omma_to_3 Posts: 3,265 Member
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    If it's not constantly monitoring your heart rate (do you have to touch it to take a reading at multiple times during your workout?), it's not going to be accurate. For most people 10 calories per minute is the upper burn for higher intensity things, though a bigger, less in shape person could top that. I'm not sure why people shy away from the chest strap. You can't even feel it and it makes for a much more accurate measure.
  • hmayo86
    hmayo86 Posts: 81 Member
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    I tried looking it up but there's not too much info on the website... Do you input personal info like height, weight, gender, etc into the app?

    I did input personal info to the app.
  • hmayo86
    hmayo86 Posts: 81 Member
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    If it's not constantly monitoring your heart rate (do you have to touch it to take a reading at multiple times during your workout?), it's not going to be accurate. For most people 10 calories per minute is the upper burn for higher intensity things, though a bigger, less in shape person could top that. I'm not sure why people shy away from the chest strap. You can't even feel it and it makes for a much more accurate measure.

    It's a constant monitor. That's why I went with the armband bc I wouldn't have to stop and check my pulse. I didn't want another monitor with a chest strap bc I didn't like the one I had previously. It wasn't that it was uncomfortable it just took forever to get the stupid thing on and if you didn't get it wet enough or got it too wet you had to take it off and start over. By the time that's all done I could've already worked out. Just seemed simpler to go with the armband.
  • oeagleo
    oeagleo Posts: 70 Member
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    I guess I can weigh in here, and give my personal experiences. I have had a Polar FT7, FT60, and an FT80, and am now using a Suunto T6D. I've found that using all of these, gives fairly consistent readings with the HRM. However, I've also started downloading the information from the Suunto into another program, Firstbeat Athlete, that actually measures the "R-R" data, (the time between heartbeats, from what I can figure), and the totals from the same download of the HRM give vastly different results. For instance, a 60 minute "cardio" workout, involving an hour on the elliptical, 3 "Planks", 3 sets of Back hyperextensions with a 25 Lb Plate, and finally 3 sets of 12 reps of "Hip Twists" on a machine with about 60 Lbs of resistance shows as 531 calories in an hour and a half. However, when I upload the same information into "Movescount.com", (the Suunto site to keep track of activities, the actual calorie count within the HRM gives a total of 1083 calories burned. I use the "Firstbeat Athlete" numbers, for a couple of reasons, it's better to underestimate than overestimate, and because of the plethora of data the HRM gives, and is analyzed within the program, I feel this is a much more accurate representation of my actual energy expenditure.
    Of course, this is only MY example, and using the tools that I have on hand, but as you can see, a lot depends on exactly HOW the data is analyzed, and presented.
    Hope that helps a bit.
    :bigsmile:
  • trexmsuee
    trexmsuee Posts: 7 Member
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    hmayo86,

    An an electrical engineer (I build bio-metric sensors, among other things) and a runner, I've been doing A LOT of research into HRM sensors lately. Comparing models, algorithms, apps, etc ... Since I use my phone for tracking my outdoor running (and music), I wanted a Bluetooth compatible HRM, so I recently purchased a Polar Bluetooth Wearlink.

    Here's a short synopsis of what I've learned (partially echoing the responses from other users):
    1) Wet the strap with saline solution before you start your workout. Ensure that the electrodes aren't being pulled or interfered with from articles of clothing.
    2) I think you have the Bluetooth version w/ the iPhone - correct? Make sure the iPhone and sensor always have close proximity to prevent data dropouts. A few seconds of lost data can greatly skew workout results.
    3) The algorithm calculation of "estimated" calories burned is done in software by the particular app you are using. Different apps will give different results! Almost all apps approach the problem the same way, but there are subtle differences. In any case, these are only estimates. To get the best calculation, the app needs gender, age, weight, height, heartrate AND the particular sport or activity. Different activities - aerobics versus treadmill versus elliptical, for example - require different mechanical effort and therefore the heartrate alone is not totally sufficient. Try different apps compatible with your monitor and compare the results.
    4) Your resting heart-rate and your maximum heartrate need to be set in the app correctly. 220-minus age IS NOT a good estimate of max HR for folks who are fit and workout regularly. This link has a good calculator which compares several of the different formula: http://www.stevenscreek.com/goodies/hr.shtml. My max HR is much higher than the simple estimate. Until I fixed this, the some of my HRM results were erroneous (long explanation required for this, I will skip for now...).

    I do agree that the numbers you observed seemed on the high side ... Let us know what you find out.

    Good luck,
  • sammyneb
    sammyneb Posts: 257
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    4) Your resting heart-rate and your maximum heartrate need to be set in the app correctly. 220-minus age IS NOT a good estimate of max HR for folks who are fit and workout regularly. This link has a good calculator which compares several of the different formula: http://www.stevenscreek.com/goodies/hr.shtml. My max HR is much higher than the simple estimate. Until I fixed this, the some of my HRM results were erroneous (long explanation required for this, I will skip for now...).

    Could you help me understand the website calculator that you provided? I have "low normal" resting heart rate of 58-59, but when I run I have a high heart rate, it can easily get into the 170's. There has been debate if I am less "fit" than I think I am or rather I just have a high heart rate (I've only been running for 1.5 years) When my heartrate gets that high, I don't feel like I'm dying, but it does wear me out. My question, is I put in my resting heartrate and then had the calculator figure my target heartrate...there are two sets of numbers, the second set is the "heart rate reserve", it says it was re-calucalted because of my resting heartrate..it gives me a much higher threashold for a heart rate...do you find that number to be more realiable?
  • cwolfman13
    cwolfman13 Posts: 41,871 Member
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    OP...definitely need something that constantly monitors heart rate. I have an FT4 and it's pretty darn accurate...I've compared it to a few different VO2 calculators after my workouts and it's usually within 10-20 calories of the VO2 calculator. I usually just take the lower number.
  • trexmsuee
    trexmsuee Posts: 7 Member
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    sammyneb,

    I'm not an expert on this, and I'm sure there are some folks who know more about the physiology than I do, for sure ... The Steven's calculator results aren't really explained very well. Heart Rate Reserve (HRR) is defined as the HRmax - HRrest. So the second set of numbers are normalized relative to HRrest.

    The information most all software packages and apps ask for is relative to % Maximum - i.e. the data in the first set of columns. Use that set of numbers, as it is by far, the most common reference.

    I really got interested in this recently because my HRmax was very low using the 220-age formula. What threw me for a loop is that Endomondo "maxed" out its readings based on my HRmax I entered into the app. This is just crappy programming, because I know my actual HR was higher. I average 20 - 26 miles a week, and I've been dropping about 2.5-3 lbs/wk for the past 10 wks.

    BTW, I have observed the "2 minutes / mile per pound rule" to be very close!

    Good luck,
  • sammyneb
    sammyneb Posts: 257
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    trexmsuee,
    Thanks for your input. I believe the 220 heart rate formula doesn't work for me. I just ran 4.2 miles with an avg. heart rate of 170...yep 170 my watch says I burned 489 calories..which I don't believe (i use the 100 calorie/mile rule)...I think if the heart rate calculator's were right..I would probably be dying right now :)

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