"The Genghis Khan warriors used to have a rule that you never talked about injury. The way it translates for me is: Don't train for what you don't want to have happen. It's like this: People say, "Oh, I can hold my breath for five minutes." I say, "I wouldn't be working on that because that might be something that you get tested on."" (Read more)
...despite that, he really works very hard on his breath holding.