Why does my watch record heart rate readings when off wrist?

[minimo3]

My series 3 records heart rate readings when it’s sitting on the table (locked) as well as when it’s on the charger. So I end up with weird readings like 130bpm at 2am at night when I’m not even wearing it. It takes readings all night long when off wrist. Is there any way to fix this?

 

[rgyiv]

I would like to know this too, it's frustrating when i see the green underglow when it's just sitting on my nightstand.

 

[oeagleo]

Same here, I think it's magic...

 

[RonFromOregon]

I've noticed this as well, but not since I updated to WatchOS 5.1.2. Which OS are you using?