I've paired my Vivoactive 3 with a Polar H10 heart monitor. When I start to record a run, should the heart monitor start recording automatically? Or do I need to start the heart monitor app as well?
Theoretically, if the H10 is already paired with the watch, it uses it to monitor during an activity, not the watch's sensor.
At least that's how it works with a VA4, which I have.
I also use a H10 during runs.
If not connected, but paired, when starting a run, the H10 connects to the watch automatically.