You all can do your own research. Moderate exercise for a limited amount of time is overall good for one's health, excessive HIIT training is really bad for older people. Like all "medicine", what is the right dose? I only ride 15-20 hours per week and do much less than an hour of intensity per week (beyond zone 2), that works for me. What works for others? Start reading and make your own decisions.
"
At low to moderate levels of exercise, there is a lower risk of AF.3,4
However, rather than a linear benefit derived from increasing levels of exercise, there appears to be a threshold beyond which increasing exposure is associated with an increased risk of AF.5-12"
https://www.acc.org/latest-in-cardio...itive-athletes