Versa underestimating HR?

[Jorgos]

hello !

looked into a review about Inspire HR that misses high intensity HR regimes. So i decided to buy the Versa: on stairs it misses quite a bit , Versa reports 105HR when actual is 138R! (via professional SPO2/HR meter)  thats 20+% error...

I suspect that is the reason for underestimating caloric expenditure...(?)(ive seen some reports of this here) 

Granted its my first day. I will try it with biking soon. 
Stairs is a short period exercise , maybe it will be more accurate in the sustained biking effort.

Other possibility to improve? i.e. i have more visible vains on the inside of my wrist. 
is it advisable to rotate the Versa 180 degrees and une it like that? any experiences? 

best regards

Moderator edit: subject updated for clarity

[NellyG]

Hi @Jorgos I have no personal expierience with wearing the Versa or other trackers on the inside of my wrist, but others report that it works well there. Give it a try and see what happens.

[SunsetRunner]

Hi, from a medical point of view it even should work more accurate as the HR sensor is nearby the radial and ulnar arteries. It does not pick up signals from veins but from the arteries. If this post is helpfull for you, see my signature. Thanks. 

[LZeeW]

@Jorgos   Placing the sensors on the inside of the wrist probably won't improve your heart rate tracking during intense exercise.  And it might be worse.  As @SunsetRunner mentioned, you have two arteries on the inside of your wrist.  But the heart rate sensor isn't over the arteries and it would be over a part of you with a number of tendons -- they scatter the light, making it harder for the detector to detect anything.

It is for this reason that Fitbit recommends wearing your Versa on the outside, farther up your arm than for day-to-day wear.  This placement reduces interference from wrist motion in intense activity.

If you are up to it, here is a link to an article that talks about the obstacles of optical heart rate monitoring.

[SunsetRunner]

Hi, if the sensor is capable of monitoring your HR right through your wrist, being not in the vicinity of arteries at all, then why shouldn't it  be possible to detect your HR when wearing it "upside down". The signal of the two arteries are much stronger than the tendons you make mention off. But all in all, this is a semantic discussion. 

[LZeeW]

@SunsetRunner   It is not semantics.  It is engineering.  The light does not pass through your wrist.  The green LED is the emitter; the two adjacent sensors detect the light that has been reflected and refracted by the soft tissue.  The data is collected from an area of a few square mm.  The radial and ulnar arteries are not involved.   Muscle, tendon and bone create more optical noise than simple soft tissue.