Got the watch 2 weeks ago, and very disappointed with the HRM performance during walks. It stays too low (around 90-100bpm, instead of the expected ~110), and what's worse - doesn't change when the heart rate goes up (e.g., going up a hill). I'm pretty sure that it's not a cadence thing since if in the middle of walking up a hill I bring up the HR widget, after a couple of seconds the HR jumps about 30bpm to 120-130bpm (but looking at the watch face with an HR field updating every second, without going into the widget, yields the same 90-100bpm). So it looks like the HRM is in some sort of battery-saving mode until actively questioned by the user.
Walking up several flights of stairs is another case where the watch fails to detect the heart rate correctly. It's an activity that raises my heart rate as well, and it's completely undetected by the watch.
HRM during runs seems accurate. I'm planning to test my theory regarding battery saving by starting a walking activity next time I walk my dogs (so the route and pace are the same), and compare the hear rates I reach. In fact, when I just got the watch, the heart rate seemed correct (and reacted to elevation changes), when walking was detected by MoveIQ, but MoveIQ would stop activities after even short pauses, so I had to turn that off (that's an issue for another thread).
Anyone noticed such problems with their vivoactive 4?
Edit: Forgot to mention - tried both wrists with the same result (including updating the wrist setting); also, the only setting that looked relevant to battery saving was the data recording interval (smart/every second), tried both with no effect.
