Ha, at first I just noticed that he ran exactly 3.14 and thought "well, that number sounds familiar." Then I thought that "irrational" was a strange way to describe running a longer distance than normal and just put the two together...
On his blog [1] he talks about running 3.14 constantly, so it's possible that he chooses to run pi miles on purpose regularly. Who knows.
e: AND called that an "irrational improvement." That must be a joke or something...