Question over HRM accuracy during strength training

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Purple_Orchid_87
Purple_Orchid_87 Posts: 517 Member
in Food and Nutrition
Just looking for some clarification. I received the following message from a friend on here, who shall remain anonymous:
Not sure if you are aware of this already, but one thing I read up about when I was using my HRM to track calories burnt during my strength training is that it will give you a vast overestimation of calories burnt. They're basically calibrated to steady-state cardio (although some of the more advanced ones can track HIIT pretty accurately as well), but when doing isolation exercises like you do during strength training, your heart rate doesn't match the number of calories actually burnt.

Just letting you know, because if your gym sessions are consisting of a fair bit of weights / sit-ups and things like that, you may not be burning as much as you think you are and eating back all your exercise calories may be slightly counter-productive.

When I go the the gym, I start my HRM the moment I step on the treadmill (i only walk, i dont run or jog) and dont look at it again until i'm walking back to the changing room.]

My gym routine normall consists of:

30 minutes walking on treadmill
3 sets of 10/15 reps on leg push
3 sets of 10/15 reps on ab curl OR 3 sets of 10 sit ups
3 sets of 10/15 reps on leg push
3 sets of 10/15 lower back exercise
3 sets of 10 reps on leg push
15 minutes walking on treadmill

The highest I ever get my HR is 171 and thats when I'm walking on an incline of 12% @ 3.5mph for just 3 minutes

So I need some clarification - my HRM often tells me I burn in excess of 800kcals, sometimes over 1,000kcals - should I be stopping my HRM when I move from treadmill to strength, and then turn it back on when I start back on the treadmill??? or should I carry on how I am???

I dont wish for this to turn into an arguement or anything over the quote because the person who told me that is very very helpful - just want to double check :o)

Replies

  • wheelieblade
    wheelieblade Posts: 323
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    what type do you have? I know polar do one that can be used for both cardio and strength training
  • Purple_Orchid_87
    Purple_Orchid_87 Posts: 517 Member
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    its just a Lloyd's Pharmacy one - wanted to start off with a not so expensive one and then if i stick with it, i will upgrade
    was kinda thinking id bail out of the lifestyle change after a few weeks but im still here
  • wheelieblade
    wheelieblade Posts: 323
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    In that case may not be so accurate for strength training I know the polar one is expensive, I don't have it
  • emsibun
    emsibun Posts: 208
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    ^^ And it's great to see you still here!

    Looking at your diary your exercise calories are very high usually which would make it very hard to eat them back as you've been advised.

    But then I don't know what kind of calories your exercise regime *should* be burning for a person with your vitals :smile:

    I hope someone can help you with this... anyone?
  • ajkat081
    ajkat081 Posts: 3
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    Which Polar version? I've got the transmitter but no watch yet and I don't know what to buy that'll give me both strength & Cardio.
  • wheelieblade
    wheelieblade Posts: 323
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    ft80 I think
  • taletreader
    taletreader Posts: 377 Member
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    You're not burning 800 calories or anywhere close, unfortunately.

    HRM calorie burns are at best estimation based on your heart rate (and the data on age, sex and weight you provide to the device), and they are *only* valid (approximately!) for aerobic workouts. Walking is an aerobic workout. Strength training isn't. The benefit of strength training isn't that you burn so many calories during the time you do the exercise, but it is what goes on afterwards, the muscle you build (or preserve from being lost when you lose weight).

    So what I'd do (or actually *do* do)

    - Only run the HRM during aerobic activities, such as (brisk) walking, cycling, running, rowing.
    - Take the calorie part of my strength training as an extra which I don't measure.

    (- I also subtract 100 calories per hour from the HRM result, to account for the calories that I'd have burned while lying on the couch, because these are already counted. Or sometimes I just divide the HRM result by two. That is, I make sure I massively underestimate my burn. This gives me an extra security if I eat back those calories, and given my basic setting is less than 1 lb/week, that works really well for me.)

    Another way of looking at it: Calorie burns from walking is about 100 cal/mile for a 180 lbs person. (You can find tables online - it varies with your weight.) At 3.5 mph you get 350 cals/h -- without an incline. Some playing with online calculators makes me think that if you're going at it REALLY strenuously with a high incline, this MAY double to something like 700/h, but probably you'll still be below. Let's say 600/h, so for 45min it would be 450 cal. That sounds a much more realistic value to me.
  • hillview2
    hillview2 Posts: 212 Member
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    Wait WHAT??? HRM doesn't work for say a bootcamp workout?? That SUCKS. Sorry to hijack
  • taletreader
    taletreader Posts: 377 Member
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    Wait WHAT??? HRM doesn't work for say a bootcamp workout?? That SUCKS. Sorry to hijack

    What do you mean, "it doesn't work"? It works just fine: it monitors your heart rate. That's *all* it does.

    For all the derived variables such as calorie burn you really really need to get spend a little time understanding how it works for your body and the devices you use to monitor it. Sorry.
  • rmqt
    rmqt Posts: 78 Member
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    (- I also subtract 100 calories per hour from the HRM result, to account for the calories that I'd have burned while lying on the couch, because these are already counted. Or sometimes I just divide the HRM result by two. That is, I make sure I massively underestimate my burn. This gives me an extra security if I eat back those calories, and given my basic setting is less than 1 lb/week, that works really well for me.)


    thank you for point out the "couch calories!" I suspect a lot of folks don't factor that in...
  • wheelieblade
    wheelieblade Posts: 323
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    I don't factor them in but don't eat all my cals back, sarah knew that tho :)
  • Purple_Orchid_87
    Purple_Orchid_87 Posts: 517 Member
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    i too dont eat my exercise kcals back - im lucky to get a NET of 1,000kcals after my workout and my dinner, and i eat a good dinner, not just like half a piece of bread

    thing for me is, as long as im moving, i dont really mind if my HRM is 100% accurate - i rarely go over my daily allowance anyway, and sometimes struggle to eat the 1200 basic - as long as my HRM is not under-estimating, i'm ok :o)

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