My resting heart rate is 44 over the past 12 months according to my Garmin watch. I’m in y early 50s, and I thint a lot of my generation never takes their watch off so that’s pretty much 365 days / 24 hours a day. 30 years ago I was riding my bike to work every day in my summer job and used to ride as hard as I could both ways - it was essentially a series of sprints between traffic lights with the occasional long draft behind a bus. I now know that would be classed as 30-40 minutes of fairly hard anaerobic exercise a day (I set off too late most mornings, being a student and all, and I just wanted to get home in the evening but I also used to try and get a higher average speed on my Cateye computer). My mum is a trained medical professional and took my resting hr with her nurses watch and it was mid 20s then. I think some of it must be genetic? I’ve always have some symptoms,of bradycardia (principally lightheartedness when I stand up) but my gp has never questioned it, and even my mum wasn’t that bothered.