Why is higher better?

[Newtripley]

Hello

Sorry if this is a silly question but I've found the higher I wear my Versa 2 above my wrist the more accurate the HR etc..I was wondering why

I've always worn any kind of timepiece quit snug on my wrist as I have quite small wrists however since having Fitbit devices Blaze, Ionic and now Versa2 I've found I get better readings if I wear it approx 1 finger width above my the wrist

I was wondering why as I would have said that wearing directly on the wrist bone where the veins etc are more prominent you would have a stronger reading

Just musing as to why😊

[JohnnyRow]

The blood flow decreases as you go further down the arm.

The sensors are sensing blood flow in the small capillaries.

[Newtripley]

Ah thank you

[JohnnyRow]

There is, or was, another brand of optical heart rate sensor worn way up above the elbow, that some said got even better results, but it was just the sensor and not full tracker with display.