I'm also considering using an HRV app, I've been struggling the last two months with power when my HR goes over 160/170 (max is about 192 odd - but haven't been there in a while). Based on the other thread I got tested for Covid, but both active and anti-body tests returned negative. My guess is that I'm a bit fatigued (prep for TransB) although nothing worse than what I've done before. But can't say for sure, I am on a 2 week break and will gauge once getting back on the bike, whether I should seek further medical advice. Some general questions if someone might be able to answer, just comparing the two apps: EliteHRV free and the HRV4Training app is R140 odd, any major differences between the two?Noted on the EliteHRV site I can use a Garmin HRM with the app but no specific mention on the HRV4 stie?Any other points to consider? Edit: For context I'm 32.