I run, but I haven't trained enough to run a marathon, or 26.219 miles.
I don't run I have arthritis but all the young people around here run marathos
Marathons go all the way back to the fabled run of Pheidippides, a messenger.  I just don't have the stamina!
I would never last a marathon but want to know all about them so I can converse with the neighbors about it
They were one of the first Olympic events in 1896, but the distance wasn't quite set until 1921.  I can run 1/2 marathon at 13.1 miles.