18.20/19.18 HR bug still here

Strange, I would suspect the opposite - you need to get a good grip on the handlebar and also pull brakes and push shifters, hence I would expect more muscle activity and increased blood flow compared to running, for example. Plus, vibration you get tends to be high-frequency compared to arm swing, so that should interfere with the HR frequency even less.

It depends on the type of the cycling activity and the cyclist itself. An inexperienced cyclist who is anxiously holding the handlebars with cramped hands, literally squeezes the blood from his forearms.

Yes, just consider how many people complain that their hands go numb on long bike rides. That's lack of blood flow just there.

No it's not, it's pressure on the nerves in the hand, specifically the Carpal Tunnel

I favour this version. If it was reduced blood flow, the riders would experience different symptoms and severe problems imho.

It's not even a matter of favor, it's literally the cause, common knowledge in cycling...that and pressure on the ulnar nerve as well on the outside of the wrist. Different fingers, different nerve pathways. Never heard of a case where hand numbness cycling was caused by blood flow.

If you do the research, this is completely incorrect, it literally has nothing to do with blood flow, it has to do with tendon movement, microvibrations, and harsh movements (same with weight lifting), etc...HR is usually more inaccurate at the beginning of a ride as the HR monitor latches on. Indoor cycling is actually one of the easiest activities for a HR tracker, but road and specifically mountain biking are much harder because of movement, not blood flow. Think how the Apple Watch detects a double tap, this is interference to HR detection.

Hi Garmin-Sierra

Please can you advise an update and ETA on this?

While this is being looked into, please can an older version of software be made avaliable so we can use the watch properly, if not please advise why not?

Here is a nice example of a completely wrong measurement during an day to day activity that should be easy to measure for the watch. I was just going for an easy walk. Normally i would not activate a sports activity for this but to showcase the problem i did now. From experience i know that this erraneous data will also be there when not manuall starting an activity - resulting in a completely messed up calculation of the daily load and all the other things the watch is doing. In the middle i made a pause where i was sitting down for a few minutes - at this point the measured WHR and HR received from my H10 began to synchronise (using a polar verity sense brings similar results).