@elbee I don’t fully agree that it’s only person related.
I’ve used several watches with optical heart rate sensors, including the Pixel Watch 3 and 4, the Galaxy Watch Ultra, and the Garmin Fenix 7X Pro. All of them provide reliable heart rate readings on my wrist without any noticeable issues.
With the Suunto Race S, and now with the Race, I still experience occasional cadence lock and workouts where heart rate is clearly underreported or not captured correctly. What’s confusing is that some activities are recorded perfectly, while others are not.
Since other brands work well for me under the same conditions, I don’t think the issue can be explained purely by individual physiology. There seems to be something specific about Suunto’s optical HR implementation or algorithms that makes it more sensitive in certain situations.
That’s what I struggle to understand. If optical heart rate measurement generally didn’t work for me, I would simply accept it and use an external sensor. But based on my experience with several other watches, optical HR clearly does work for me. That’s why I find these inconsistent results on the Race and Race S difficult to explain.