Here is a mildly interesting annecdote. I hiked up the Smuggler trail yesterday, the same one that’s described on page 122 of the Yellow Book.
A couple of things were different, It was fall, not winter. And, heartbreakingly, no beloved Aengus, the Weimaraner, doing 360’s in the snow. He died years ago; we miss him every single day.

But here’s the nice part. It took a few seconds less to do it than it did then (cheating, since it’s easier without snow) and my heart rates were generally a hair higher than the original ones (good) and my recovery rate was 44, not 37 (good). My max was a couple of beats lower (bad but that’s on the biological time line…nothing to be done, really). So maybe I am a teeny bit younger than I was six years ago. Okay, that’s not true but not a hell of a lot older, either…just as promised, years ago. AND there were not a ton of 75 year old chaps out there either.