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Trusting fitbit numbers

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aliciab307
aliciab307 Posts: 370 Member
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24, F
196lbs~
37.6%bf~
Lift 4-5x/wk
Zumba 2x/wk
Walk 10-22k/day

Ok so I have the fbChargeHR. And for the past 2 wks my avg burn is 4.1k-wk 1, 4k-wk 2.

What is the margin of error for fitbit, if anyone knows? I'm wondering how much I should trust FB numbers. Lifting sessions are about 30-60 mins, zumba is about 45-60 mins

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  • aliciab307
    aliciab307 Posts: 370 Member
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    Bump
  • 2essie
    2essie Posts: 2,866 Member
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    If you join the fitbit group you might find more people with the answer for you if you post your question there. Just a thought.
  • aliciab307
    aliciab307 Posts: 370 Member
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    Thx. I'll check there
  • heybales
    heybales Posts: 18,842 Member
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    The calorie burn for the lifting should be manually entered, as HR based formula is going to inflate it.
    HRM formula for calorie burn is only valid for steady-state aerobic exercise, same HR for 2-4 min.
    Lifting if done right is just opposite of that.

    For your other stuff, if the HRM formula is good for you, could be decent enough.

    Here's study on a much nicer Polar HRM, with self-tests for needed stats, and the results using lab measured stats.

    http://www.myfitnesspal.com/topics/show/459580-polar-hrm-calorie-burn-estimate-accuracy-study

    And no - I doubt Fitbit is using formula nearly as good as Polar's.

    Otherwise, the device underestimates for daily calorie burn outside of exercise.
    It assumes sleeping level calorie burn for all non-moving time - BMR.
    But when awake you burn more - RMR.
    When standing not moving you burn even more.
    When digesting/processing food you burn more, about 10% of calories eaten.
    So outside of exercise - underestimated.

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