Coevett wrote:
And if they were running close to 13:00 at 25, they should be able to run sub 15:00 with ease at 45.
I used to think that too, but that's not the way it works most of the time. People burn out. I know quite a few Masters runners who I can crush with my lame 17 minute 5k that were well under 15 in their early 20s.
One guy in particular made it to his early 30s still running mid-15s, only to be reduced to struggling to break 20 in his early 50s. Seriously. He never stopped running. He just slowed and then fell off a cliff, it seemed. Another guy I know, whom this website had a thread about once, ran in college and got under 14 minutes, and was running 18-mid by his early 40s. These things happen.