Just experienced the same issue as AlexCH after a 40 min interval session on a rowing machine. Recorded a 61 bpm average heart rate! Tried a lot of different wrist positions to no avail. I have had reasonably accurate readings from running and cycling and suspect there is something about the rowing machine that prevents a good reading, could be flexed wrists or something to do with position of wrists relative to heart on an erg. Quite annoying as bought it to track heart rate but the data is useless!
Will try cleaning it and doing a gentle warm up to try and get a lock on heart rate first.
I shaved my wrist, put on the Vivosport super tight and got on the gym bike again. I pushed myself to max for 60 minutes, the bike showed pulse between 150 - 190. That sound about right as I am 55.
Vivo showed a pulse between 70-100, once jumping to 125.
I get a believable reading from Vivo from low pulse activities, but when I really push myself the device is a joke. You can't speak of accuracy. Looks like the thing does not notice my raised pulse at all.
I'm thinking of switching to Polar with a possible Oura ring.
Thanks. I am thinking of donating my to my kid and getting a Polar Vantage that seems to get more accurate readings. I did a lighter set today: hour of indoor bike + hour of weights. Surprisingly Vivosport picked up my pulse up to 150. This never happened before! Well, I'll take some time figuring out a replacement. Polar Vantage costs 200€ and I can get a decent smart watch for that price.
Got on the phone to Garmin support about this issue and they asked me to send them some example activities with bad heart rate readings. I sent them 4. They have asked me to restore factory settings on the device and try again. Anyone tried this? I'm not holding out much hope as I don't think I've changed any/many of the settings in the first place.