First of all, I understand that no wrist-worn fitness tracker is going to be 100% precise. I use mine less to get hard numbers, and more to see trends. That being said, I'm noticing some odd numbers during recorded exercises.
I went for a quick walk this afternoon (1.33 miles), and my Charge 5 recorded it as 101 bpm average (1 minute fat burn), which for the type of walk, that seems reasonable. It calculated an average calorie burn rate of about 9 calories/min. Total calorie burn for the 30 minutes was 278. An exercise calculator at Omni Calculator (omnicalculator.com) estimates 217 calories. Their heart rate calculator estimates about 313 calories burned. So the FitBit calculation seems to be in the right range.
Later in the day, I went for a bicycle ride. I rode 10 miles over the course of an hour, with an average heart rate of 117 bpm (52 mins fat burn, 2 mins cardio). However, the app also shows 9 calories/min over the course of the hour. Calories burned for the entire hour was 562, which lines up with the per-minute numbers. Using the Omni calculators, they give an exercise estimate at 1199 calories, and heart rate estimate at 785 calories. Even going by the conservative second estimate, the FitBit calculation is WAY off.
Intuitively, it feels like both of them can't be right. An hour of bicycling has only twice the impact of a half an hour of walking? Is there something that I don't have set up properly in the app? One thing I did note was that the above calorie count totals were showing on the FitBit summary screen when I hit finish on the Charge and the exercise was closed out, which makes it appear as if the calorie calculation is happening on the tracker, and not in the app. It does not appear that the app appears to try and correct any of the calculations after the fact.
Curiously, it also does detect that there is activity going on, as my daily record shows. It shows both the walking activity in the afternoon, and the bicycling in the evening. It just thinks that they're both equal activity levels:
Anybody got any ideas here? Do I need to reset the device? Am I missing a software update? I am currently running firmware version 57.20001.188.58.
I'm going to try not actively recording my next exercise sessions (I have auto-detect exercise turned off). I'll see if that has any impact on it.
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