You remember this quote from Bernard Lagat where he stated that the #1 reason for declining performances with ongoing age are mainly caused by a lack of motivation, becoming parents, ... - short: becoming lazy ?
He supported this quote by his stellar 2013 performances. Sure, a little speed has vanished but his endurance HAS to be still there, running sub13 at age 38.
Most of the message board laughed at it and put the "on" stamp on Bernard.
Now, there is Haile Gebrselassie, running sub 61 while being in front the whole race with no one supporting his effort. Keeping up with Mo Farah and Kenenisa Bekele. In a 1500 things would look different but since speed vanished his ENDURANCE still has to be there. Hes not far from his 59min shape. Given that speed got a little worse his endurance has to be the SAME at least.
Disregard PEDs, if they take it they have been taking it for their whole career, so its a constant.
The interesting fact is the age. Sub 13 at 38 (at least...) and sub 61 at 45+(dont argue on this one, he IS this old) is impressive.
Anyone got scientific proof on that, especially a "endurance improvement curve" with ongoing age would be interesting for some late starters. Can you still train your endurance the same when you pick up the sport at 20, 25 or 30 like younger HS kids?