I have been using my old wrist base garmin fenix 3 heart rate monitor for a few months now as a way to make sure I do not overdo my easy runs. It took a while to get used to the slower centurion pace plod. Quite often, I thought my garmin must be wrong, but usually, on closer checking of the data, it was probably right, and it was just taking longer than I was hoping for my body and legs to adapt.