Hi @Rthorsen It is not comparable with HRV measurements made from a chest strap. I am pretty sure the Sense watch measure HRV on the blood from reliable. I have both tools available and my hypothese is that the measured, or estimated HRV on the blood flow is less than the HRV when measuring electrical pulses from the heart. It will be smoothen out due to physics, resistance and elasticity of the veins and blood.
My Sense give me HRV readings between 20 and 30 and I am not worried. The same applies with the RHR being measured differently by Fitbit compared to other methods, some take the very lowest observed HR during night, some use the morning instant reading, some average HR over a 5 min period, some take HR when sitting up during the day etc. What is important is that you measure it in exactly the same way each time to compare it with previous days results.
In my opinion this is the advantage with fitbit and other wrist devices, it is measured automatically and calculated in the same way each day, goes for both HRV and HR.
I recommend to ignore posts using HRV measurements from chest straps and other devices, there will be a too large variation. The same goes for some of the publicized studies on HRV, which measure the electrical pulses and often use 24h average results.
