Overly Generous HRM?

kikicr
kikicr Posts: 10 Member
in Fitness and Exercise
Hi. Are HRM's quite accurate?

I have been trying to lose weight, following a calorie control plan (that's how I ended in MFP, :smile: kinda following Jillian Michaels meals) and increased my exercise by adding 2 classes a week (bodypump/bodyattack) I go 3 more days to the gym but to do a general workout: threadmill, bike, crosstrainer and weights.

I got a fitbit and according to it the calories I burn at the threadmill, bike or crosstrainer are quite the same, which sounds good, but I dont know what can be my calorie burn during abs and weights, but I dont do much of these anaerobics exercises, I spend more time during aerobic trainning. I aim for 500 cals according to the machines.

Yesterday I got a HRM and I used it this morning for the first time. I thought I had set it to " start" when I was at the threadmill, but realised after 18 mins that I hadnt pressed the actual "start" button, so I pressed it there and then. Finished my threadmill work (threadmill clocked 400 cal,similar to fitbit) , did some floor abdominals, lifted some weights, and went to the crosstrainer (115 cals, similar lo fitbit reading) and stopped the HRM; and when I checked the calories burned it said 701 !!! is that possible? which it would probably had been over 800 if I had started it at the beggining of my threadmill run/walk !

Im eating 1400-1500 cals daily, accoding to my TDEE, but in 4 weks I have only lost 1 Kg ! lots of weight fluctuations in between !! it's kinda frustrating ! could I be undereating? (sounds to good to be true).:tongue:

Replies

  • Lina4Lina
    Lina4Lina Posts: 712 Member
    What is the brand? Does it have a chest strap?

    You might have to adjust it, Mine was overly generous until I went into the website configuration for it and adjusted the settings. Now it is much more accurate.

    HRMs are just estimates but you may need to fiddle to get a better estimate.
  • AnninStPaul
    AnninStPaul Posts: 1,372 Member
    What is the brand? Does it have a chest strap?

    You might have to adjust it, Mine was overly generous until I went into the website configuration for it and adjusted the settings. Now it is much more accurate.

    HRMs are just estimates but you may need to fiddle to get a better estimate.

    this - you have to set it for your weight, etc to get a good estimate
  • kikicr
    kikicr Posts: 10 Member
    It's a polar FT7 and I did go through the setting with my weight, height, age, etc.

    ETA: It does have a chest strap, and I dont have to look at the wrist part cos the heart rate comes up on the gym machines (syncs with the machines too, but calories totally different)
  • Lina4Lina
    Lina4Lina Posts: 712 Member
    Does it give you an average HR ? Generally, HRM are considered mostly accurate estimates for cardio. If you were doing floor exercises and weights, you may or may not have been working in the cardiovascular range. I didn't catch initially that you wanted it for weights and for weights, it really isn't accurate unless you are doing some continuous weight routine.
  • kikicr
    kikicr Posts: 10 Member
    Linani, I did 1 hour in the threadmill running/walking , about 15 mins of weights and floor abs, because it was just a short while I kept the HRM ON, and 15 mins at the crosstrainer.
  • bombedpop
    bombedpop Posts: 2,227 Member
    If you are going straight from cardio to weights, your heart rate is still up from the cardio and the HRM burn will be higher. Try doing the weights first, then cardio - you will see different HRM burn results as your HR will be lower while doing the weights.
  • Wabbit05
    Wabbit05 Posts: 434 Member
    I average 100 calories per 10 minutes according to my HRM, obviously depending on how hard I'm going.
  • Serenstar75
    Serenstar75 Posts: 258 Member
    I was going to say, it shouldn't become suddenly inaccurate if you're doing weights versus cardio. Heart rate is heart rate. But what the last poster stated about elevated heart rate due to cardio first then weights is true. If you want that kind of burn, this order can work. I do it either way, but usually if I do cardio first, it's a short session.
  • 2hobbit1
    2hobbit1 Posts: 820 Member
    http://www.myfitnesspal.com/topics/show/548645-setup-polar-hrm-for-more-accurate-calorie-burn-for-known-bmr?hl=hrm+adjustment+for+women

    haybales shows you how to set your polar up for a more accurate read - check it out.
  • kikicr
    kikicr Posts: 10 Member
    http://www.myfitnesspal.com/topics/show/548645-setup-polar-hrm-for-more-accurate-calorie-burn-for-known-bmr?hl=hrm+adjustment+for+women

    haybales shows you how to set your polar up for a more accurate read - check it out.

    Thanks !
  • recriger
    recriger Posts: 245 Member
    Using an HRM for weights is not accurate. It will correctly read the heart rate, but it won't attribute it correctly. The heart rate itself doesn't burn the calories, it is just an indicator that work is being done. The type of work will tell us if we are burning more calories. Weight training increases the heart rate due to an increase in pressure in the chest, this burns more calories, but not in a linear track with the heart beat. when we do cardio our heart rate increases because we are needing to pump more oxygen (in blood) to the muscles, this action does increase calorie burn in a linear fashion.

    I always think of it like the spedometer in the car. The spedometer reads how fast the tires are spinning, not how fast the car is moving. It just happens to be labeled for the latter. If you hit the accelerator on a wet or slick day and the tires spin you will see the spedometer peg out, but the vehicle hasn't moved. This would be the heart rate increase from weight training. Heart goes nuts but the calories aren't burning.

    Perhaps that only makes sense to me because I have my own context in mind. :embarassed:

    Anyhow I have found that the calculations on MFP for weight training are within 10-20 calories per session (for me at least) when compared to my weight loss chart, so I just use their calculations. I use the HRM for all cardio.
  • Lina4Lina
    Lina4Lina Posts: 712 Member
    I was going to say, it shouldn't become suddenly inaccurate if you're doing weights versus cardio. Heart rate is heart rate. But what the last poster stated about elevated heart rate due to cardio first then weights is true. If you want that kind of burn, this order can work. I do it either way, but usually if I do cardio first, it's a short session.

    Well the HR is accurate but not the calorie burned. The research on HR predicting calorie burned resulted in only accurate results when the HR is at a certain level. If the level is below that then, the calorie burned isn't considered an accurate estimate.

    And I can imagine if someone is working out for 2 hours then 700/800 calorie burn wouldn't be surprising.
  • kikicr
    kikicr Posts: 10 Member
    Thanks for all the imput. What I'll do next time is to use it only for cardio, stop it while I do weights, and see what happens. :smile:
  • heybales
    heybales Posts: 18,842 Member
    I always think of it like the spedometer in the car. The spedometer reads how fast the tires are spinning, not how fast the car is moving. It just happens to be labeled for the latter. If you hit the accelerator on a wet or slick day and the tires spin you will see the spedometer peg out, but the vehicle hasn't moved. This would be the heart rate increase from weight training. Heart goes nuts but the calories aren't burning.

    Perhaps that only makes sense to me because I have my own context in mind. :embarassed:

    I love illustrations, and that one is great, even if no one really noticed that's what is happening. I'll have to use it if you don't mind.

    Even on cars where the speedometer ties into a sensor on the camshaft, if you have transmission problems you can have the speed appearing to go all over the place, but no movement.

    Or as was my problem, bad alternator, bad sensor power, bad sensor readings, transmission trying to adjust to bad readings, mis-shifting - same effect. Lovely.
  • crimsoncat
    crimsoncat Posts: 457 Member
    To double check the heart rate's calculator accuracy you can manually calculate the calories burned based on a online calc. For the most accurate results you'll need to:

    A. Calc your V02max: http://www.shapesense.com/fitness-exercise/calculators/vo2max-calculator.aspx#restingheartrate
    B. Calc your calories burned with a KNOWN V02max: http://www.shapesense.com/fitness-exercise/calculators/heart-rate-based-calorie-burn-calculator.aspx
    C. Convert from gross to net calories: http://www.shapesense.com/fitness-exercise/calculators/net-versus-gross-calorie-burn-conversion-calculator.aspx

    Using my heart rate monitor's data (a basic HR-100c only shows the heart rate, not cal)I got that my burn on the elliptical today was right about the same as the MPF calorie measurement for time on the elliptical. I have also calculated my heart rate at 4mph walking and got a lower cal burn than MFP claimed for me. . I figured that was proof I was at least in the right ball park.
  • heybales
    heybales Posts: 18,842 Member
    To double check the heart rate's calculator accuracy you can manually calculate the calories burned based on a online calc. For the most accurate results you'll need to:

    A. Calc your V02max: http://www.shapesense.com/fitness-exercise/calculators/vo2max-calculator.aspx#restingheartrate
    B. Calc your calories burned with a KNOWN V02max: http://www.shapesense.com/fitness-exercise/calculators/heart-rate-based-calorie-burn-calculator.aspx
    C. Convert from gross to net calories: http://www.shapesense.com/fitness-exercise/calculators/net-versus-gross-calorie-burn-conversion-calculator.aspx

    Using my heart rate monitor's data (a basic HR-100c only shows the heart rate, not cal)I got that my burn on the elliptical today was right about the same as the MPF calorie measurement for time on the elliptical. I have also calculated my heart rate at 4mph walking and got a lower cal burn than MFP claimed for me. . I figured that was proof I was at least in the right ball park.

    Great site for explaining the cardiorespiratory system to someone.

    But that's not going to be the best way really.

    If you are concerned about the HRM's calculation of VO2max being off for it's use in it's calculations, you've only traded one set of estimates for another.
    Those VO2max formula's are merely estimates too. And not great ones.

    Actually, there has been a study that showed a formula was more accurate than those submaximal tests.

    http://www.myfitnesspal.com/topics/show/577839-hrm-s-with-vo2max-stat-improve-calorie-estimate

    So now you are starting with a bad foundation of VO2max that could easily be 10 off, I know they are from my tested stat. Both directions too.

    Actually, the best test is going to be walking 3-4 mph as you stated, level, for probably 30 min. MFP and treadmill and this site all using the same very accurate formula for that effort and calorie burn. If the HRM is off, it's because it is estimating the wrong VO2max or bigger effect, the HRmax stat is set wrong.
    http://www.exrx.net/Calculators/WalkRunMETs.html

    http://www.ncbi.nlm.nih.gov/pubmed/15570150

    Oh, and the HRM is going to be reporting Gross calorie burn, none of them do Net. Net is only important in diet schemes so as not to eat back too much.

    So the HRM shouldn't be near NET calories burned, but gross. You'll have to manually do it.

    Of course, if walking, can just use the walking calculator and select net for better eatback. Sadly MFP doesn't do that.

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