I don't understand the mechanics of how my Garmin was fooled that evening but it definitely corresponds to the period that I was feeling cold. As for 180 being

I don't understand the mechanics of how my Garmin was fooled that evening but it definitely corresponds to the period that I was feeling cold. As for 180 being possible for my wife--nope. We aren't youngsters and she was carrying on a conversation at the time. It was reading her arm movement, not her heart. I got myself a separate heart rate strap but Fitbit doesn't support them and she's just wearing it for the bonus the insurance company gives. (Which is set to such a ridiculously low threshold that you would have to be awfully sedentary to not reach it--in practice it translates to wear a fitness tracker, get $10/month.)