Difference in calorie count between two HRM's?

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beefolks
beefolks Posts: 21 Member
in Fitness and Exercise
I have a Precor 546 elliptical that I use at home. It is set up such that if I wear a Polar HRM, the Precor will automatically calculate how many calories were burned. (It asks for weight and age, but no other factors.)

I recently bought a new Polar ft7 HRM (chest strap, watch, etc.) I set it up with my info.

I wore the ft7 chest strap on my most recent workout. The Precor said I burned 380 calories. The ft7 watch says I burned 215.

This seems like a significant difference to me. Does anyone have any insight?

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  • wolfchild59
    wolfchild59 Posts: 2,608 Member
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    The calorie counters on machines don't factor in gender. As a female, the machines will be a little high since they are calibrated for a general average, which includes men using the machine. Since men burn more calories than women, you won't get accurate, personal readouts from it. Go by your HRM that you wore.
  • beefolks
    beefolks Posts: 21 Member
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    That's a good point, though ill be sorry not to count those calories anymore. Thanks!
  • Azdak
    Azdak Posts: 8,281 Member
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    The heart rate displays on fitness equipment are there to display your heart rate on the console, nothing more. They are not integrated in any way to the calorie display.

    That's because machines and HRMs estimate calories completely differently.

    Machines measure your actual workload and use that (along with weight) to estimate calories. HRMs estimate calories based on HR response--actually they estimate calories based on how closely your exercise HR fits an algorithm developed primarily from treadmill exercising. Since an HRM has no idea what exercise you are doing or how hard you are actually working, it must make assumptions about the nature of your exercise. If what you are doing matches those assumptions (e.g. steady-state cardiovascular exercise, with accurate HRmax, HRrest, and VO2max programmed into the device), the accuracy of the HRM increases. If they don't match, then HRMs are less accurate or not accurate at all.

    Theoretically, the machine numbers SHOULD be more accurate, since they are measuring the actual work being performed. However, machines are only as accurate as the underlying equations programmed into their consoles. For activities such as walking or running, the equations are well established and pretty accurate. However, there are no standard equations for cross trainers/elliptical trainers. Each manufacturer has their own design and so they must derive their own machine-specific equations for estimating calories. It takes time, money, and resources to do that, so the quality of the equations varies widely. A lot of the elliptical equations overestimate calories--in my experience, usually by 25% or more.

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