As with all things measured from a wrist worn sensor, and ove the course of the order of a decade of essentially continuous wearing, I've found that the device

As with all things measured from a wrist worn sensor, and ove the course of the order of a decade of essentially continuous wearing, I've found that the device may be wrong (and completely off the mark at times) but is also mostly right most of the time. I don't expect anything else for a device I wear loose most of the time (and snug+proper placement when working out) yet it still gives me eerily accurate metrics to work with.