Kingfisher wrote on Mar 31^st, 2011 at 9:15pm:

Are all you nose breathing advocates seriously thinking that one could run a mile at a faster pace by not opening their mouth. I am very skeptical. I will continue to experiment with the nose breathing but I still am very skeptical.

While I am in decent shape I am in no way qualified to instruct anyone who is as superbly fit as KF seems to be. But rather, since I was the originator of the post, I would seek to clarify only lest what I advocate be misconstrued and thus be misunderstood.

What has worked for me and countless thousands of climbers is called "pressure breathing". Essentially it is breathing in through the nose and pursing the lips and exhaling forcefully through the mouth. You are doing it right when it is accompanied by a swooshing sound. It is fine in theory that pursing your lips while forcefully exhaling through your mouth creates some sort of back pressure. I am dubious of that. What I do know is that it expels a lot of spent air in a hurry and from way down deep. In comes another draft through my nose, I pause a second or so to let it provide the benefit and then it is forcefully removed through the mouth.

It is in fact when I feel starved for O2 and I'm workin hard that I employ this and it usually sets the ship right.

The step method I advocate for special usage is called the "rest step". It is common climbing methodology. If you are the investigative sort google "pressure breathing" or "rest step" to get the skinny on both of these potentially useful methods.