Me and my wife have recently been using HRM Pro. Unfortunately, it underestimates the intensity minutes and recovery time. We did tests using only the HRM Pro while cycling, and the next time on the same route, the Fenix 5 with the HRM Pro paired. For me, the difference is about 35% in the case of intensity minutes (eg 215 F5 + HRM Pro vs 147 HRM Pro), but for my wife the difference is huge (179 F5 + HRM Pro vs 56 HRM Pro). In addition, my wife's recovery time is almost always equal to 0 when using only HRM Pro. Sometimes HRM Pro counts single hours, but for the activities I mentioned, in the case of HRM Pro it was 0 hours, and in the case of Fenix 5 + HRM Pro it was 4 days! 0 hour vs 4 days?! Really??? I know that even on the same route the effort is different, but the measurements are extremely different.
Why is the HRM Pro belt such a terrible calculation of intensity minutes and recovery time?