Nutella1 wrote:
Without time to prepare/train for it? 10%. Not more. Example: Edison Pena, the Chilean Miler. Didn't he run 5:12 or so?
If they have half a year to train for it? Theoretically 1/3. In reality, most wouldn't stick with it therefore I say 20%.
A data point. My wife ran a marathon 4 years ago... she trained for several months, with usually one or two ~10km runs during the week and a longer run at the weekend. She's mid-40s, in good health, not overweight. She ended up running a few minutes under 5 hours on a *very* hot day (and did keep running the whole way). I'm sure it would have been faster on a cooler day, although hard to say how much faster.