Early in college, I started to notice that my athletic reaction time had dropped, and I realized it was because I wasn't putting in as many hours playing sports as I had at Westtown.
Then soon after I graduated from Earlham, not just my reaction time, but my skills in all sports had slightly declined for the same reason.
When I got to my 30's, it became harder and harder to keep up with "kids" in their teens and 20's, and I decided it was because I wasn't running as much as I once had.
Then in my 40's, when playing soccer and ice hockey, I had lost a step or three compared to younger players, I felt like all I needed to do was get in shape and I'd be right back where I had been in my 20's or 30's.
Now that I'm in my mid-50's, splitting wood and repeatedly picking the wood and wedges off up off the ground for a few hours requires frequent rest breaks, and makes me think for the first time that it isn't just a matter of being out of shape, but //shudder// it may just be that I'm getting old.