I've had the Sense for more than a year now and I am going to say it again: Nice watch, but a fail in so many other ways.
Yesterday morning, I had not even gotten out of bed yet except to visit the bathroom twice - it's only about 15 steps from my bed and does not involve any stair climbing. Nevertheless, I managed to accumulate 12 Zone Minutes - six of them in Fat Burn zone and the other six in Cardio!
My resting heartrate is in the low 60's and dips to the upper 50's overnight. Walking on a treadmill at 4.0mph, my rate gets up to the mid-90s (as measured with a Polar chest strap) and around 120 when at a slow 4.5 - 5.0 mph jog. I know what a cardio heartrate feels like; there is no way my heart was beating in that range for six minutes without my being aware of it!
I wear the watch reasonably tight, so it was not flopping around on my wrist.
This has been a constant problem with the Fitbit Sense. As such, I have pretty much zero faith in the data it provides me. About the only function that I am confidant in is the time of day.
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