Originally Posted by downtube42

Age is sneaky. It comes at you so slowly you don't notice, and it comes at you in a lot of different ways. Thinking back to my uncles as they aged, they were all surprised to find themselves old and physically unable to do what they'd always done. You'd think we all see it as it hits us, but that doesn't appear to be the case.

I have data from all my brevets from aged 50 when I started, to now at 63. Brevets are not races, and time wasting varies a lot, but here's the fastest 200k from each year since 2010:

Indiana - flat to rolling hills
50 8:55
51 9:33
52 8:25
53 8:34
54 8:40
moved to west Texas - flat
55 7:55
56 8:03
move to Oregon - climby
57 8:38
58 10:55 (COVID year, only 1)
59 9:03
60 8:58
61 8:58
63 8:43

That's not a clear downward trend. But I've gotten a lot wiser about riding distance.