Polar HRM calories burned....question

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Emily3907
Emily3907 Posts: 1,461 Member
in Fitness and Exercise
I learned long ago to not trust the MFP calorie burns. I caught on early that they are way overestimated.

I recently joined a wellness center that has my workouts programmed into a key fob that includes my stats (height, weight, age, etc.). This gives me a calorie burn at the end of my workout. I have been using this amount to log into MFP.

But, today I pulled out my Polar HRM (chest strap/watch - FT7), updated my stats and used this at the gym to see what kind of burn it gave me. My gym burn was 550 calories, but my Polar burn was 456 calories.

So, now I am questioning if I should be wearing my HRM during workouts and using that burn instead for more accurate logging.

Typically, I try to only eat back about 50% of my calories, but I go by a weekly calorie goal so sometimes my exercise calories are used for alcohol or weekend shenanigans....because sometimes a girl needs a cupcake. I want to make sure I am getting as close to accurate as I can (obviously I know none are perfect) with my burns.

So, would you trust the Polar HRM burn in my circumstances?

Here is today's workout - I am currently at 268 pounds, 5'4". (Yeah, I have a lot to lose.)

Polar HRM - 456 calories
Gym tracker - 550 calories

Weights - Various weights (legs, arms and core) including 8 weight machines, kettlebell squats and free weight side bends (2 sets for each at 12-15 reps)
Treadmill - 35 mins at various grades from 3% to 9% at a speed of 2.5 to 3.3

Replies

  • sarahshinks2233
    sarahshinks2233 Posts: 55 Member
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    How are the calories measured on the kettlebell? I am not 100 percent familiar with the key fobs but I believe they plug into the machine and use the machine estimate of calorie burn... If that's true, the machine may be over estimating which happens pretty frequently. It also may be that the HRM slipped and wasn't tracking for part of the workout, can you see in the report graph?
  • Lizarking
    Lizarking Posts: 507 Member
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    heart rate monitors aren't great, and they're particularly awful for any kind of anaerobic exercise.
  • Emily3907
    Emily3907 Posts: 1,461 Member
    edited May 2017
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    sarahshinks2233 wrote: »
    How are the calories measured on the kettlebell? I am not 100 percent familiar with the key fobs but I believe they plug into the machine and use the machine estimate of calorie burn... If that's true, the machine may be over estimating which happens pretty frequently. It also may be that the HRM slipped and wasn't tracking for part of the workout, can you see in the report graph?

    For anything not machine related (like free weights of any kind), I choose the exercise (so kettlebell front squats) in the app, number of sets, weight and reps into my app (which is connected to the fob/gym info) and it adds to the overall workout.

    Also, I checked the HRM results and it was constantly recording, no gaps or slips.
  • NorthCascades
    NorthCascades Posts: 10,970 Member
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    Do you have a reason to think one or the other is more accurate? It's probably that both ways of guessing occasionally get close, but neither one has any real insight into it.
  • sijomial
    sijomial Posts: 19,811 Member
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    Heart rate tells you nothing useful about calorie burns from weights - it can only count heartbeats and not calories (energy remember). No I wouldn't give it any credence in the slightest.

    Even for cardio HRMs can be wildly inaccurate. With your stats (sorry to be blunt!) it's likely you are an outlier too.

    How does this gym tracker/fob purport to measure your calories output? What data does it pick up?
  • Emily3907
    Emily3907 Posts: 1,461 Member
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    NorthCascades wrote: »
    Do you have a reason to think one or the other is more accurate? It's probably that both ways of guessing occasionally get close, but neither one has any real insight into it.

    I would say, I prefer to believe in the lowest estimate, only because I don't want to over estimate. If anything, I would probably believe the HRM in this case, only because it is a constant monitoring source. Whereas, an app estimating my burns, without real time data, makes me a little more cautious.

    To be completely honest, I don't really know what to believe! LOL
  • NorthCascades
    NorthCascades Posts: 10,970 Member
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    If you have a watch, you'll always know what time it is. If you have two, you'll never be sure.
  • Emily3907
    Emily3907 Posts: 1,461 Member
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    sijomial wrote: »
    Heart rate tells you nothing useful about calorie burns from weights - it can only count heartbeats and not calories (energy remember). No I wouldn't give it any credence in the slightest.

    Even for cardio HRMs can be wildly inaccurate. With your stats (sorry to be blunt!) it's likely you are an outlier too.

    How does this gym tracker/fob purport to measure your calories output? What data does it pick up?

    The only data it picks up is my stats (height, weight, age, etc) and then what I do at the gym. So, how much I lift, how many sets and reps. Plus, any cardio I do.

    How it gets a calorie burn from that is not very clear.
  • Emily3907
    Emily3907 Posts: 1,461 Member
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    NorthCascades wrote: »
    If you have a watch, you'll always know what time it is. If you have two, you'll never be sure.

    This is true!! LOL

    I always lean to the lesser of burns, only because I do not want to over estimate. Even then, I really try to stick to only eating about 1/2 of any exercise calories (sometimes less, sometimes more).

    It is just so hard to trust any of these devices.

    I guess I just need to watch how my weight loss goes and gauge from there. So far, I am averaging about 1-1.5 lbs per week loss.
  • sijomial
    sijomial Posts: 19,811 Member
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    Emily3907 wrote: »
    NorthCascades wrote: »
    If you have a watch, you'll always know what time it is. If you have two, you'll never be sure.

    This is true!! LOL

    I always lean to the lesser of burns, only because I do not want to over estimate. Even then, I really try to stick to only eating about 1/2 of any exercise calories (sometimes less, sometimes more).

    It is just so hard to trust any of these devices.

    I guess I just need to watch how my weight loss goes and gauge from there. So far, I am averaging about 1-1.5 lbs per week loss.

    Perfect!
    In the end you can be inaccurate on one or both sides of the CICO equation and still be successful if you are prepared to make adjustments based on actual results over time.
  • Azdak
    Azdak Posts: 8,281 Member
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    The polar number is more accurate, but in this case it is as much by chance as anything else. Your key fob system is almost certainly overestimating any non-cardio exercise by a significantly greater amount than the polar.

    At your weight, you should be able to eat 1800-2000 cals per day, which is a decent amount of food, not bother with the exercise cals, and still lose weight. Just a thought if you want to simplify things.

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