I've recently measured ~40 bpm when I'm sleeping and mid 40s-low 50s when I'm up and not moving (sit still on a chair). I never had heart rate this low, even compared to my active duty time when I had baseline heart rate of mid 50s, when I weighed 167lbs and ran a 1/2 marathon like nobody's business. Now I weigh 175 lbs, which is down from 185 since this May and been sustaining since June for a little bit over a month. All workouts I've been doing is running couple of miles a day and increased my distance to 2-3 miles a day in past 10 days, which is shorter than what I did when I was an active duty. I suspect combination of weight loss, no weight training, and reinstating running collectively affect my heart rate. I'm still in my 20s and got out of service just 2-3 years ago so I don't think aging would be the primary factor here. But my concern come from that I am wayyy slower than my active duty time (running ~8:30/mi now vs ~6:30/mi then vs ~7:10 pre-Army but I was 150lbs), while my average heart rate when I'm running is relatively high at ~175 (max out at ~187 after sprinting out last .1 mi).
I've been using my Charge 4 (dominant wrist) and Apple Watch Series 5 (other wrist) to cross ref and both of them show quite constant results.
Myself is a student in a healthcare field and consulting to a physician would be the ONLY way to figure out what's really happening but I'd like to share this with the Fitbit community and hear your opinions/experiences so feel free to talk!
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