also sport in the early 1900's was an activity pretty much only very rich people had the luxury of participating in.
one of the reasons i heard that roger bannister only trained on his lunch break by doing 10 x 1/4 with a 200 jog in between 4 days a week and 1 day a week 3 x 1 and a half miles wiles with a 400-800 jog between each is because at that time (1954) it was considered bad sportsmanship to train more than 30 minutes up to an hour 4-5 days a week, though there were rumors bannister got in some night runs to help his base.
so basically the superior training has produced superior times over the years and in 100 - 200 years the letsrun posters will probably say why did it take so long to do things like break 1:40 for the 800, or 2 hours for the marathon and the answer will still be advanced training hass improved times.