High heart rate, low calorie burn, why?

SouthernCountryGirl
SouthernCountryGirl Posts: 195 Member
in Health and Weight Loss
Why does a person burn less calories with a higher heart rate? Example, I swam for 24 minutes (vigorous laps back and forth), average heart rate of 94, calorie burn 161. Yet I rode a bike, vigorous, up/down slopes roads, 23 minutes, average heart rate of 123, burn 64 calories. (Per my Apple Watch) Why is there such a large difference in the numbers? I thought a higher heart rate produced a higher burn?

Replies

  • mmapags
    mmapags Posts: 8,934 Member
    MikePTY wrote: »
    Heart rate and calorie burns are not related to one another. This is why HRMs can often be inaccurate in calorie estimates. I can't comment on the accuracy of either of those burns, but only that it is quite possible to burn more calories doing an exercise with a lower heart rate than one with a higher heart rate.

    What MIke said ^. Heart rate is only used as a proxy for calorie burns for an estimation specifically for steady state cardio activities like running and biking. But they approximate using a formula and it is quite often inaccurate. I'm not sure how your apple watch calculates calories but that is also somewhat of an estimation, albeit a closer one due to it adapting to your data over time (I know Fitbits do this and I'm assuming apple watch does). The only real way to measure calorie burns is to measure Mets but that is rarely practical.
  • jjpptt2
    jjpptt2 Posts: 5,650 Member
    MikePTY wrote: »
    Heart rate and calorie burns are not related to one another.

    Correct.

    There are some assumptions and correlations you can make in some situations, but in most cases HR and calorie burns aren't closely related.

    Calories burned is a function of work done... of energy burned. That may or may not be reflected in HR. Swimming has MUCH more resistance than does cycling, and uses more muscles to do the work, so I'm nto surprised you got a higher burn from swimming.
  • Azdak
    Azdak Posts: 8,281 Member
    jjpptt2 wrote: »
    MikePTY wrote: »
    Heart rate and calorie burns are not related to one another.

    Correct.

    There are some assumptions and correlations you can make in some situations, but in most cases HR and calorie burns aren't closely related.

    Calories burned is a function of work done... of energy burned. That may or may not be reflected in HR. Swimming has MUCH more resistance than does cycling, and uses more muscles to do the work, so I'm nto surprised you got a higher burn from swimming.

    My question in reading the OP was that most HRMs rely primarily on heart rate to estimate calorie burn. They can’t really measure specific workload. That’s why you get the big burns from things like hot yoga or sitting in a sauna.

    Plus, because of body position, heart rate is often lower when swimming for the same MET level. So you would not expect an HRM to ever give a higher calorie burn with a lower heart rate.

    Unless the Apple Watch uses a different algorithm for swimming. Which is possible since Apple has designed the watch to be worn during swimming workouts.
  • CSARdiver
    CSARdiver Posts: 6,252 Member
    Caloric output is largely dependent upon mass and to a much lesser degree effort. Many people misinterpret the HR calculations - deliberately in some cases as these tools are marketed for this purpose.

    These calculations are pretty accurate if you mimic the baseline algorithms - long steady state cardio from running, biking, or swimming. Anything else the accuracy decreases rapidly.

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