Your training and ride pacing is wrong. Not an age issue. I'm closing in on 64.
How often are you doing HIIT? What are the sessions like?
How often do you ride 2 hours or more in zone 2?
What is your longest ride in hours per week and at what intensity?
Do you log your rides into a training application? If so, what is your chronic training load? What was your TSB after the 200K?
The amount of recovery time depends on how fit one is. Normally, a 200k would not do much to me but I did one 6 weeks ago that sent my TSB to -65 and I gave it 11 days of easy riding in zone 2 before even thinking of doing any intervals. It takes a long time to build and one must be consistent in training riding almost every day for many, many months or perhaps a year or two.
Last edited by GhostRider62; 04-28-22 at 06:31 AM.