"Second wind is a phenomenon in distance running, such as marathons or road running, whereby an athlete who is too out of breath and tired to continue suddenly finds the strength to press on at top performance with less exertion. The feeling may be similar to that of a "runner's high", the most obvious difference being that the runner's high occurs after the race is over.[1] Some scientists believe the second wind to be a result of the body finding the proper balance of oxygen to counteract the buildup of lactic acid in the muscles.[2] Others claim second winds are due to endorphin production, while still others believe it to be purely psychological."

Not that I know anything about second wind, but 5:23 isn't that great of a mile time.

Wow. Someone at my school won first in state and he's 12 btw and got like in the top 200 in the junior olympics i think. I wonder if he's experienced stuff like second wind and runner's high.