Apple Watch and heart rate

[blcarney88]

I was borrowing my son's Apple Watch 3 to see if I liked it. I loved that the C2 with PM5 automatically detected heart rate from the watch and displayed it in ErgData. This allowed me to to stay in a particular heart rate zone.

I bought a new Apple Watch 9. It does not consistently detect & display heart rate in ErgData. It will show 0 for the first few minutes, then 101 for a few minutes when I know it should be closer to 120 from previous experience. The numbers may be different each time, and the length of time spent at any given heart rate are different.

I've done a small bit of forum searching but most posts seem to be older. I've seen discussion about disabling certain things like going into the Health app & disabling ErgData from writing workouts, but that didn't help & may actually have made it worse.
(Please no talk about why I should use a heart rate strap instead. I will be sticking with the watch.)

[jamesg]

I use an oxymeter to see HR during interval rests, since my belt-watch and belt-PM show not pressure pulses but electric impulses, which can be two or three for each heart beat.

In any case I've seen that HR training theory is correct, when aerobic: there's fixed ratio between HR range in use and Watts. Mine is just over 2, so my W tells me what my HR is; not that I don't know anyway.

[gcanyon]

I had the same issue with my original Apple Watch maybe 6 years ago. It’s been better recently, but I don’t have a current model; mine is an SE. when it was a thing I would start my workout a minute before rowing to let it get its bearings.