"Chronic excessive exercise has been consistently associated with increased risks of atrial fibrillation (AF)"
Happened to me. I am convinced my Afib was/is the result of my hard charging CrossFit type workouts, especially as I aged. At 64 it all went to shit. Took nearly a year and a half to fully recover to a point where I could have a decent workout. Not too much hard cardio type workouts these days, especially for duration. 2-3 days a week in the gym and maybe one of those is what I would call intense. Most everything is resistance training with the occasional heavy bag/shadow boxing thrown in, but never more than 20 minutes of that. At 70+ it's about management of working with what you have. The days pf PR's are long gone.