I have noticed a couple of runners in my area who are well past the age of 50 and are tearing it up on the masters running scene. These runners are able to set PRs (or close to lifetime bests) well into their 50's.
Normally when you see very fast times over age 50, the runner falls into 1 of 2 categories. 1) They were exceptional runners in their prime and while they have slowed down somewhat with age, they are still exceptional relative to their peers (Bill Rodgers is a great example of this). Or 2) the runner got a late start in life and is still developing their aerobic system.
I have noticed 2 or 3 runners in my area who do not fit either of these two categories. They trained hard for several decades and ran many races in their 30's and 40's. They were good, but not great. Now into their mid to late 50's, they are running times that will potentially get them national rankings and are near or past their lifetime best times.
Have any of you personally encountered a runner like this? If so, what do you or they attribute their relative surge in performance to?