I think people are losing track of Wayne's point. You don't *need* to breath while swimming, as long as the duration is less than 40 seconds. He didn't say anything about *wanting* to take a breath. I'm guessing the pain of not breathing would be enough of a distraction to make it worthwhile to breath (a little bit) during the 50.
Have there been any studies about the body's response to *wanting* air? (Any stress responses, that would reduce muscular effort?) Or is it entirely in the head?