Heart rate monitors are not calorie monitors.

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NorthCascades
NorthCascades Posts: 10,970 Member
in Fitness and Exercise
Heart rate monitors are sensors that measure your pulse (how quickly your heart beats), and sometimes your R-R intervals (when your heart beats, variations in the rhythm).

These are training tools, meant to help people exercise at a specific intensity, to help people pace themselves during long events, and as a way to judge the quality of a workout after the fact.

They can also guess how many calories you've burned, but that's not what they're for; it's like using the oven as a space heater instead of to cook your food. It'll work, basically, but it's not ideal.

Here are some things that will raise your heart rate:

* Sickness
* Caffeine, energy drinks, nicotine
* Fear, stress, anxiety - fight or flight response
* Dehydration
* Being too hot or cold
* Lots of medical conditions
* Exercise

Your heart rate monitor doesn't know how much coffee you've had or what your mood is like today. It just knows how fast your heart is beating.

Exercise burns calories because your muscles are doing work, which takes energy. It's not your heart burning most of the calories. If you're a runner, most of your burn comes from what your legs are doing.

Calorie burns from exercise can be measured, or they can be guessed. Measuring is hard and expensive so most people don't do it. And that's ok, estimates are usually good enough, especially with the other tools we have available to us.

Sometimes heart rates are a good way to estimate energy use, but a lot of the time they're not. For things like walking and running, simple physics rules. It takes so much energy to move this much weight that much distance, adjusting for hilliness. For weight lifting, your heart rate is completely unrelated to your energy use, you're better off with a formula. It's things like cycling, Nordic skiing, and rowing, where an HRM is most useful for estimating energy use, because there are so many variables with unknown values (eg were you pedaling or coasting, going with the current or into the wind, etc).

Replies

  • Michael190lbs
    Michael190lbs Posts: 1,510 Member
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    but its only $7.77 http://www.ebay.com/bhp/heart-rate-monitor-and-calorie-counter--- great read and make sense!!
  • Mycophilia
    Mycophilia Posts: 1,225 Member
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    I approve of this post.
    vv86utr2ho1t.jpg
  • successgal1
    successgal1 Posts: 996 Member
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    Very true. I have the fitbit charge HR, I wear it day and night. I watch it when cycling so I don't over stress my heart. Its nice to see the average heart rate go down as weight goes down and fitness goes up. A very useful tool.

    For calorie burn I find it falls completely in line with what folks say around here about MFP estimates ... "only eat back half your calories from exercise". Using that mantra there is room for errors/overestimates.

    I do however find it fascinating that the calorie burn using my fitbit for 70 minutes of cycling almost 100% matches the endomondo GPS estimate, and they are not synced together.

    My fitbit tracks as "activity" when I care for the hooves of a horse. The horse is getting special treatments and the bending and holding of the hoof squishes my fat stomach and my heart rate goes up, so does my breathing. I suppose at most its an isometric exercise. I take those "earned" calories with a grain of salt, and look forward to the day that my fitbit ignores that work, which would mean the belly fat is gone!

    So, as said, its a tool. There are so many tools it can be confusing until you figure out exactly how they work, and when and why to use them.
  • Machka9
    Machka9 Posts: 24,880 Member
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    I wore my HRM on a number of my rides (cycling) and made some discoveries ... although I was riding the same speed and at the same perceived effort or the same terrain (flat), my heart rate was consistently about 10 beats higher when I cycled in the city in traffic than it was when I cycled out in the country.

    Was I burning more calories in the city? Nope. It's just that city traffic stresses me a bit.


  • powered85
    powered85 Posts: 297 Member
    edited January 2017
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    So curious as I know you have a Fenix3 - do you find the watch is more accurate w/o wearing a hrm for calculating high cardio recorded exercise? Appears it follows closer to the METs values w/o a hrm
  • AnvilHead
    AnvilHead Posts: 18,344 Member
    edited January 2017
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    Just adding @Azdak 's blog entry on this because it's a great read also: http://www.myfitnesspal.com/blog/Azdak/view/the-real-facts-about-hrms-and-calories-what-you-need-to-know-before-purchasing-an-hrm-or-using-one-21472
  • Noreenmarie1234
    Noreenmarie1234 Posts: 7,493 Member
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    Yes this. My HRM says I burn barely any calories because I have a very very low HR and it takes A LOT to get it up and up for a long time.
  • Michael190lbs
    Michael190lbs Posts: 1,510 Member
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    Noreenmarie1234 wrote: »
    Yes this. My HRM says I burn barely any calories because I have a very very low HR and it takes A LOT to get it up and up for a long time.

    Right there with you My HR is mid 50's I can ride a bike 18-21 MPH for 50 min and barely get to 120HR average
  • NorthCascades
    NorthCascades Posts: 10,970 Member
    edited January 2017
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    powered85 wrote: »
    So curious as I know you have a Fenix3 - do you find the watch is more accurate w/o wearing a hrm for calculating high cardio recorded exercise? Appears it follows closer to the METs values w/o a hrm

    For riding a bike, the way it determines how many calories I've burned doesn't even look at my heart rate data. (I wear a chest strap anyway for other/fitness purposes.)

    I have pedals on my bike that use pressure sensors (like a bathroom scale) to measure how much torque I'm applying, and motion sensors to measure how often I'm applying it. With those two things, my Fenix 3 knows how much energy I'm putting into the bike. And human efficiency on a bike falls into a pretty narrow range. So this gets me to within 5 % of the gospel truth without knowing my heart rate or age or weight - just how much work I did.

    Nothing like that exists for cross country skiing. And you can't use a formula or rule of thumb like you can for walking or running, because some miles don't take any work at all and others take a lot. So I take a "trust, but verify" approach to what my Garmin says about this, also weighing myself every day, etc.

    I did an experiment this weekend, without meaning to. I skied basically the same route with the same level of (perceived) exertion, once with my chest strap, and one day I forgot it so had to rely on the wrist heart rate sensor. I got wildly different answers:

    Saturday: 429 kCal/hour, 4 hours recovery, 1 new speed record (wrist sensor)
    https://connect.garmin.com/modern/activity/1536290485

    Sunday: 750 kCal/hour, 53 hours recovery, 2 new speed records (chest strap)
    https://connect.garmin.com/modern/activity/1538136970
  • powered85
    powered85 Posts: 297 Member
    edited March 2017
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    I thought about this some more lately around which value would provide the best estimate for caloric burn; realizing nothing is perfect.

    So using the Fenix3 paired with a HRM it uses the firstbeat technology algorithm to calculate calories. Without a HRM it appears to be using METs tables. METs values end up with a higher caloric burn for the same exercise.

    Eg. a 5 mile run gives me ~520 calories at typical pace wearing a HRM. Without HRM its in the mid 600's or more (calculates by weight/age/height etc pace I'm presuming).

    One thing that the HRM lacks is perceived effort prior to reaching a somewhat steady-state HR during the given exercise. Running is a good example where I'll be running for almost a mile before my HR gets up near the burn zone. So a good chunk of effort is happening but due to the low HR during the initial run. Caloric estimates based on pure HR could be much less than reality especially during the "warm up" time where your HR is still rising to a somewhat consistent BPM.

    I'm going to look more at using the HRM for training and less for logging calories against MFP as a trial. Perhaps using the "corrected METs" values are a bit closer to reality?

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