Frozen heart rate at start of workout.

Does this also happen, of you use the default Apple Workout app?

Does your watch recognise your pulse if you use the Heart Rate app before starting the workout?

My Apple Watch Ultra 2 only loses the Heart Rate, if it is sitting not far enough from the wrist. For a workout I will have to move it 1-2cm further away than usual. The weight of the watch pushes it towards the wrist during the movement of the arm, and it loses contact.

My investigation has gone from support, to Genius Bar, to Lead Genius @ the Bar, back to Phone Support tier 2 and is now with the engineers. I should have a response from them in the next couple days and I will post. They pulled all the logs from phone and watch and had me video myself showing heart rate in the heart rate app and workout app at the same time, with the workout app frozen in the 40's while the heart rate app could fluctuate as I make my heartrate go up and down. I do have Polar Verity Sense and the H10 chest strap. Both report normal HR during workouts and in the Polar Flow and Polar Beat app if I am not logged into iCloud. The second my workouts end and the date shares with AppleHealth and is logged as a workout in the workouts app, the data goes weird, and a workout with an average HR of 144 goes to avg HR of 56...with huges sections flatlined. It is definatly a system issue and not a hardware issue. If I use a phone and watch that are brand new and not restored from backups and not logged into icloud, everything is fine. As soon as I log into iCloud, it behaves this way until I wipe the phone and watch and start over

Try to start an Outdoor Run, using the built in Workout App, to rule out a software issue when 3rd party apps are trying to read and import the data.

Start an outdoor run workout on Apple Watch - Apple Support

I have this exact same issue and it started around the latest OS/IOS release. When I start the workout app, or trail forks app or Ride with GPS, the heart rate is correct for literally one half second and then drops to 48 to 52 bpm and freezes there for the whole workout. Yet the "heart rate" app will show a correct heart rate at that same moment if I toggle to that app. I have been on the phone with apple and they tried everything and have not been able to solve this for me. I have two other Polar heart rate monitors (H10 strap and Verity) that I use to override the HRM on the watch and they will all record correct in the heart rate app on the watch (confirming that no green lights are scanning my wrist from the actual watch), but they all freeze at 48 to 52 (Same thing happens with the new AirPods Pro 3 even when they are the only heart rate source. So it is clearly not a hardware issue. If another apple person tells me to clean the sensors after I tell them it happens with three different HRM's, I am going to scream.

Does this also happen if you start an Outdoor Walk, using the Apple Workout app?

Did you try to wear the watch on your other wrist?

Let Apple Techs know about this by using the Feedback link, to make them aware of this problem.

Feedback - Apple Watch - Apple

I had this issue on my Garmin Forerunner, until they updated the software, but never experienced this on my Series 5 or now on the Ultra 2.

But since this happens on two Apple Watches, this is really a strange coincidence.

Can you try to let another person use one of the watches to compare the results?

Has anyone found a solution for this yet? I’ve got two different Apple Watches and both had similar problems when I pair it with RunKeeper. The HR tracking may or may not start at the beginning, but usually not. After a while it might start, but even then after several KM into my run, it suddenly flatlines again for quite some time. It is more common than not to have flat HR indications on the app afterward. Very frustrating, especially when I need to see my HR when going up a hill or interval portion of my workout.

Has anyone seen this problem using a Garmin watch? I’m also thinking of switching to a chest monitor… but hate the idea of having to wear a strap.