After running competitively in high school and for a year in college, way back in the late 1960s and early 1970s, I gave it up until 12 years ago. When I got back into running, all my races were of the 5k-5 mile variety (except for an 800m at the Drake Relays in 2001).
Despite all that time off, missing pounding the streets, I am now in my mid-50s and encountering injuries with greater regularity. Right now, I'm trying to exercise and train through an iffy knee situation.
Thus, I found a National Public Radio report (Monday) about retiring from running of particular interest.
Here is the link.