I am fortunate to have several doctors (I have many potential life threatening conditions) who all either support or do not object to high level cycling and running; I am aware that I can no longer ride for hours at 22-23 mph as I did in my 40's but do push myself to the limits at least twice on weekends on 2-4 hour group rides. Mondays I just rest. During the week I do power intervals and either endurance intervals or recovery intervals two days a week. Recently I added some coaching and have experienced PR's on Strava beating times back to 2013 when I started using the software. It just seems if one is willing to do the work then loss of fitness happens much more slowly. Before covid I went to the gym once a week to do weight machines and spin classes. I have just pulled my old free weights out of the attic and am trying to put together a home gym. Although I am currently getting faster I am no longer riding 150-200 mi per week. Since I started using Training Peaks I train 6 days a week for shorter periods.