Have you heard of a slang (俗語) "when pigs fly" or "when pigs have wings"? Pigs are big and heavy, even have wings on them they are still too heavy to fly. It means something (or an event) impossible to happen. This marathon is one of the largest "1st time marathoner" marathon in USA. They even have special divisions for heavy runners (male/female) over 200lbs. So it is kind of a encouragment to these runners. Also in the old days Cincinnati was a pig trade town.
The fireflighter actually didn't involved with that fire. He intended to run the marathon by wearing 75 lbs of gears and uniform. He was doing it as a charity event. At mile 10, he stopped and performed CPR to a heart attack runner.