How can the Fenix 6 measure my heart rate while in a pocket?

I keep my Fenix 6 in my pocket instead than on my wrist when I do certain activities, typically in the chest pocket of a fleece jacket (for example, while rock climbing to prevent scratching the glass or when ice climbing because I don't have access to my wrist with gloves and many layers of clothing).

However, I noticed that the Fenix keeps measuring my heart rate and the readings seem to make sense: high when I am climbing and lower when I am at a belay station for example. Notice taht I don't use an HR strap, but the sensor on the watch seems to be measuring my HR in some way that is somewhat consistent.

Any explanation? Can the sensor work measuring my HR on my chest thought two layers of fleece? I am puzzled.

0 Frankysour over 3 years ago

Not sure how to answer the question but curios...

Next time try putting it the other way around, sensor facing outside, see if there is difference

0 KrapfenKringel over 3 years ago

When I lost my strap I had it in my jeans pocket, sensor facing my leg. It also worked, guess the sensor is good enough to shine through a thin layer of fabric...after all it also shines through the skin.

0 livesimply79 over 3 years ago in reply to Frankysour

Good point. I usually don't rely on the wrist sensor for heart rate because I don't find it accurate enough, but the readings make sense here.

I am wondering if besides the sensor it uses some sort of logic to estimate heart rates based on some other data...

0 subra over 3 years ago

The filament of your fleece jacket may reflect the OHR light.

It's like this thread

https://forums.garmin.com/outdoor-recreation/outdoor-recreation/f/fenix-6-series/207863/my-garmin-fenix-6-and-table-heart-rate?pifragment-464=2#pifragment-464=1

0 Pierrotsc over 3 years ago

same thing happened to me. Now i wear in on my wrist instead of my pocket :)

0 livesimply79 over 3 years ago in reply to subra

Thanks. I am very skeptical of these readings (I don't trust any reading from the wrist sensor in general, even more in this scenario), and I thought the sensor could detect if it were on skin or not (and stop recording if it were not on skin). What is puzzling is that the readings are coherent with me moving or being at rest: I guess that when I am moving, it detects the fabric moving and calculated a higher HR. Anyway, wrist HR monitors are practical, but not very accurate, and this is another confirmation of it. I wish the sensor could tell when it is on skin or on fabric.

0 livesimply79 over 3 years ago in reply to Pierrotsc

Unfortunately, wearing the watch on your wrist is very impractical when climbing: when rock climbing you need to use your wrist and you would quickly damage the watch, when alpine or ice climbing the layers of clothing make the watch pretty much inaccessible.