As a result of the Ionic recall, I recently purchased a Fitbit Sense. I have found that there is a significant difference in calorie counts between one and the other when cycling.
(1) During similar bike trips of 30-40 miles, and similar duration, the burn rates are much lower in the Sense that they are in the Ionic:
Ionic: 50-70 calories burnt per traveled mile.
Sense: 10-25 calories burnt per traveled mile.
This is not a single case, but a systematic difference for different trips.
(2) I did a second experiment: During a 45 mile trip, I wore the Fitbit Sense and the Ionic at the same time. The results were:
Ionic: 51.1 calories burnt per traveled mile.
Sense: 10.0 calories burnt per traveled mile.
Note that all personal parameters are the same in the Sense and in the Ionic: weight, height, dominant arm, etc.
I have not noticed differences in calories burnt when I walk, or in the "background" calorie burn. But for cycling, the differences are too large to ignore. I infer that there is either a hardware issue (sensor) or a software one (error in algorithm to compute calories while biking).
I will appreciate opinions, but more than anything, if someone at Fitbit reads this, please offer a solution.
For those interested, here is a table with more details:
| | Date | Steps | Total Cal | Bike time | Bike distance | Bike cal | cal/mi |
| | | | | | | | |
| Ionic | 12/20/2021 | 4650 | 3866 | 3 h 26 m | 33 | 2239 | 67.85 |
| Ionic | 12/28/2021 | 4000 | 3371 | 3 h 46 m | 36.1 | 1795 | 49.72 |
| Ionic | 3/21/2022 | 6292 | 3913 | 4 h 44 m | 39 | 2247 | 57.62 |
| | | | | | | | |
| Sense | 4/2/2022 | 6056 | 2223 | 1 h 50 m | 16 | 300 | 18.75 |
| Sense | 4/13/2022 | 6780 | 3279 | 4 h 10 m | 42 | 1012 | 24.10 |
| Sense | 4/20/2022 | 5300 | 2509 | 4 h 35 m | 45 | 452 | 10.04 |
| Ionic | 4/20/2022 | | | | 45 | 2300 | 51.11 |
