Pheidippides is said to have run at about 23 rides and hour when he dashed through the Marathon plateau to get the news of Greek victory over Persians to Athens. A ride is said to be 4 stadia, which is in turn 6 plethra(if I remember it correctly). I read this from an college physics textbook(Halliday & Resnick) and tried to find out what a ride is in Greek, but I couldn't find one. A [face=SPIonic]i(/ppeuma[/face] is what I think to be a candidate. But the dictionary definitions don't mention anything about it as a unit of distance.
http://www.smaphysics.ca/phys30s/int30s/convert2.html See Prob. 2