Pick a " talented " 7th grader and slowly build his mileage up thru out high school and college.
He could live a hermit lifestyle, run on dirt trails, have a massage weekly or whatever, and took pre hab and everything to the max
If he was to live this isolated, Quentin Cassidy like lifestyle, how many mile a week could he run and remain healthy by his 30th bday? What would his race results be like?