Wearing Fitbit with hardware in wrist from prior injury, does it affect the readings?

[RoninD86]

Hello, 

I just got the charge 5,  I had a motorcycle injury years ago which has left me with permanent hardware in one of my wrists/forearm. Metal plate, screws, kwire, etc. I have wondered would this have any effect on the various readings? I’ve switched placement back n forth at times, generally don’t seem to notice much of a change, though with different fitbits I have seemed to get different readings , even wearing two different models at the same time, one on each wrist to see what they say. Does anyone know the science behind the sensors and how it reads and gets results, if having medical hardware would effect it?

[N8teGee]

Hi @RoninD86, welcome to the community.

I wouldn't have thought it would make a difference, as long as the blood flow is normal. I think from your own test you've proven it to be the case. 

This Fitbit health article (here) covers a bit on how optical heart rate sensors work. Although I'm sure a more technical analysis can be found if you want more details.