Calorie burn discrepancy between Fitbit Charge HR and chest strap heart rate monitor
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bossfan55
Posts: 11 Member
I just bought the Charge HR last week, and wanted to compare the HR and calorie burn to my chest strap HRM. So, I did some workouts with both - the chest strap recording in MapMyFitness, and the Fitbit tracking through the Fitbit app. I ran for 28 minutes. The chest strap showed 152 average BPM and 388 calories. The Fitbit showed 153 average BPM and 288 calories. Also, for a 55 minute P90X workout, the chest strap showed 96 BPM and 287 calories burned, and the Fitbit showed 93 BPM and 155 calories. I now understand that, for lots of reasons, the P90X calorie burn on the Fitbit may not be accurate. But, the discrepancy in the calories on the run confuses me. The heart rate readings were nearly identical, but the calorie burn was substantially different. I thought it might be that the HRM calculates the entire burn, while the Fitbit "filters out" the BMR and only gives a net calorie burn, but one of the members of this board say that the Fitbit also calculates a total burn (and, my BMR is about 1 cal/minute, so even if you add 28 calories to the Fitbit burn it's still very different). Any thoughts as to the reason for the discrepancy?
Thanks!
Thanks!
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Replies
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Since I am older than you, short, female, with probably have a lot less muscle than you, do not run, walking and some dance aerobics for my exercise, I doubt your BMR is 1 cal/min. as mine averages a tad over 2 cal/per min. Since you are a runner, I am assume you have no serious health issues to impact your burn.
If you're using a Polar there is no way to know how they count calories, it is proprietary info. so it would be difficult to say why.
One thing to check is the stride length for the Fitbit, that might account for some of it? The FAQ tells you how to adjust that.
I have used a chest strap and now the Charge HR. Believe me I burn more calories with the charge HR on all days, so not overly concerned about a half hour activity even if it is "exercise". Just do your thing and let the Charge HR track your burn.0 -
Good points and good advice - thanks. On the BMR, plugging my stats (59, 5'8, 140) into a bunch of online calculators, I get about 1400 cal/day, which is 1 cal/min, which seems consistent with my sleeping calorie burn that the Fitbit logs. I'll check the stride length and see what happens.retirehappy wrote: »Since I am older than you, short, female, with probably have a lot less muscle than you, do not run, walking and some dance aerobics for my exercise, I doubt your BMR is 1 cal/min. as mine averages a tad over 2 cal/per min. Since you are a runner, I am assume you have no serious health issues to impact your burn.
If you're using a Polar there is no way to know how they count calories, it is proprietary info. so it would be difficult to say why.
One thing to check is the stride length for the Fitbit, that might account for some of it? The FAQ tells you how to adjust that.
I have used a chest strap and now the Charge HR. Believe me I burn more calories with the charge HR on all days, so not overly concerned about a half hour activity even if it is "exercise". Just do your thing and let the Charge HR track your burn.0 -
All HRM's likely use their own proprietary formula - or pay Firstbeat for use of theirs.
Polar ain't sharing theirs with no one, so if comparing to Polar, yes different.
Cheaper Polars makes lots of assumptions like Fitbit may be making, better Polars have the self-tests and are better estimates.
If Timex - they are notorious for inflated calorie burn estimates, and don't even have enough stats for decent estimate anyway.
Fitbit would be wise to base running on HR and pace as average, which Garmin does on some HRM's, but I can't discern unless someone is willing to do some interesting tests.
You might test both HRM's though, while testing that stride length too. See which one is better.
http://community.myfitnesspal.com/en/discussion/774337/how-to-test-hrm-for-how-accurate-calorie-burn-is/p10 -
All HRM's likely use their own proprietary formula - or pay Firstbeat for use of theirs.
Polar ain't sharing theirs with no one, so if comparing to Polar, yes different.
Cheaper Polars makes lots of assumptions like Fitbit may be making, better Polars have the self-tests and are better estimates.
If Timex - they are notorious for inflated calorie burn estimates, and don't even have enough stats for decent estimate anyway.
Fitbit would be wise to base running on HR and pace as average, which Garmin does on some HRM's, but I can't discern unless someone is willing to do some interesting tests.
You might test both HRM's though, while testing that stride length too. See which one is better.
http://community.myfitnesspal.com/en/discussion/774337/how-to-test-hrm-for-how-accurate-calorie-burn-is/p1
Thanks for the info. It's actual an Armour39 HRM (an Under Armour product), that I always figured had an accurate algorithm - I usually get about 350-400 cal on a 3 mile run, which I've always assumed to be correct based on various calculators and on MapMyFitness and MFP estimates without the monitor. But, my assumptions may be wrong. I'll definitely check out your suggestions.
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What stats does the Armour39 have on you?
And I doubt they paid for a good HRM - was it over $90 USD?0 -
See, the Timex HRM's for longest time had weight and DOB, that was it, and DOB was merely used to set the different zones by assuming the HRmax was 220-age.
You can't get a decent calorie burn estimate from weight and HR, not at all. There are others equally as bad.
So was curious what stats the Armour even asked for. Sounds like it wouldn't be worse than cheaper Polar at least - depending of course on what algorithms they used.0
