Eh oh wrote:
The first guy's response is good, but it's a long shot in any case. Too slow or not, 70 mpw is significant and if you've been training at that mileage for a while, it might be hard to improve a full minute more. For a typical guy who runs a PB of 14:00 as a senior, I would probably expect a PR of 14:20-14:40 as a freshman. That doesn't mean that a 15 flat freshman can't do it, but you'd be an outlier.
I am sorry to disagree with you but in my mind this is absolutely not correct... wanting to improve from 15 to sub 14 in 4 years is not asking all that much... stay healthy, train consistently, train with any good program and I'd say improving a little over a minute is fairly standard practice.