Apparently many people hyperventilate while running - who knew?
http://www.runnatural.co.uk/page.asp?ID=269&PID=54
I do know that during sprint or hill intervals sometimes I'll get into a place where "in two - out two" isn't enough but "in two - out one" or "in one - out one" is too much. So I do know how hyperventilation hurts performance. Unfortunately the article doesn't say anything about how to address that.
