Does your HRM report higher or lower than MFP?

lasia221
lasia221 Posts: 19 Member
edited September 22 in Fitness and Exercise
From what I'd read here, it usually sounds like those that use a HRM find that they burned more calories than MFP was saying.

I was shocked today to find out that this wasn't true for me. But, it is my first time using my Polar FT7. Maybe the electrodes weren't wet enough, maybe it wasn't tight enough, maybe it wasn't in the right spot. I don't know.

The exercise I do at home is step aerobics, using the Wii balance board because I have really bad knees and the high step up of a regular step aerobics board would kill me. But still, even just ten minutes and I'm huffing/puffing/hiccuping and sweating. I usually can only manage 10-minute bursts for now, I rest for a little and then do 10 more.

MFP had two aerobics that I was using depending on how hard I worked (what songs I matched) - aerobics, low impact and aerobics, general. Wow. Big difference!! HRM says 83 cals; Aerobics, low impact says 92 and Aerobics, general says 120! Ugh I've been overeating bc some days I come very close to eating my exact limit.

Replies

  • princessmikayla5
    princessmikayla5 Posts: 140 Member
    My HRM always says way more than MFP does. I worry that my HRM isn't accurate and I'm overeating!
  • slieber
    slieber Posts: 765 Member
    Mine is usually way lower than MFP. I use the FT40. And used the F6 before, which also said cals were lower than MFP.
  • Stewie316
    Stewie316 Posts: 266 Member
    My HRM always say's I burn less than MFP or any other online calculator.
  • vtboomamj
    vtboomamj Posts: 4
    My HRM always says I've burned less calories that MFP reports. I have a polar RS-800 which takes my weight, age, and heart rate into the equation. I'm curious what other people are using, and what type of fitness level they would rate themselves as. MFP only takes time, (maybe age), and weight into account. All HRM (should) take at the very least, time, weight, age, and HR into account. I'm actually curious why your HRM would report lower calories. What type do you have? How long have you been using it? What would you say your average Heart rate is when you are working out?
  • PJilly
    PJilly Posts: 22,178 Member
    I have a Polar F4, and it gave me calorie burns lower than MFP's estimates as well. I'd already been losing successfully using the MFP estimates, so I just stuck with those. They're all just educated guesses anyway.
  • ChellieIrish
    ChellieIrish Posts: 593 Member
    I have the Polar F6 and I'm the opposite as per the results below :wink:

    Based on my HRM I burned 768 cals (92mins) today while out walking with my Bichon Frise on & off leash :bigsmile:

    but I just checked and MFP shows

    Walking dog - 359
    Brisk 3.5 - 414
    Walking @ 4 - 545
    Walking @ 4.5 - 686
  • taletreader
    taletreader Posts: 377 Member
    My HRM is usually slightly above what the gym machines say (+20% or so) and both are way under what MFP says. I usually log the smaller of the number from the gym machines or HRM.

    Also, +- 30% is NOT a large difference -- you can't expect these devices to give you accurate calorie counts at all, and I'd warn of relying on them down to the last 100 cals or even less. Consumed calories, for aerobic exercise, depends on oxygen used, which a HRM can't measure directly at all. Yes, it correlates with the heart rate, but there's also your fitness level! Take an example. Let's say you run for a mile:

    - On Nov 1 you do it for the first time. Your heart rate maxes out. Your HRM logs a number of calories, say X.
    - On Dec 1, you've gotten fitter and are used to the exercise. Let's say you haven't lost any weight and run at the same speed. That means that the energy expenditure is the same as on Nov 1 (ie, the energy it takes to move your body at the speed you're running at for 1 mile -- no change in the work that you've accomplished). But you'll be fitter, so your heart rate will not be as high, and your HRM will log a lower number of calories Y < X.

    Does this mean you've burnt fewer calories? NO. Likely the HRM will over-estimate while you're unfit, but really, it's not the appropriate tool if you want to make an exact science out of it. It's a great tool for *monitoring your heart rate* in order to stay within whatever zone you're targetting and also gauging your fitness. The calories are useful in comparison -- if it shows twice as many today as yesterday, for aerobic exercise, you've probably worked out twice as hard and consumed twice as many, but how many in the absolute is a rough approximation.

    So the bottom line is to figure out what works for you. If you log the HRM number, eat back the exercise calories, and lose the expected weight, great! You're doing it right, but there's luck involved in the HRM measurement being accurate. Personally, I only eat a few of the exercise calories right now, to be conservative about it. +- 30% in exercise calories should not put you over your goal.
  • lasia221
    lasia221 Posts: 19 Member
    Thanks for the input.
    I'd consider myself to be fairly unfit - I'm certainly getting better, but at 245 with fibromyalgia I'm no spring chicken here.

    MFP warns you not to go too low, and so perhaps I'm taking that to heart too much. If it gives me the warning when I've gone under 1200 (my w/out exercise limit is 1280), then shouldn't I also be concerned if the 1280 + cals burned - what I eat is less than 1200?
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