FWIW.......

My experience is the air breathing style I gleaned from some climbers I had become acquainted with while working at Mt Rainier has served me best when it is a situation where one must work hard for a sustained span of time.

I have proven it over and over to myself that it does indeed work. When I find myself struggling on a steep incline or fighting a nasty headwind on my bike or ascending a 3 mile switchback trail (plenty such slogs out west) if I discipline myself to breathe in through my nose and blow hard out my mouth. I calm down and typically can sustain a much longer and steadier pace than if I am huffin and puffin just through my mouth. Scientifically not sure what the dif is but all I know is it works........common practice amongst climbers even in the thin air.

It might not be for everybody, I just know it works and works well for me.

Good one Joe about the "extra protein"  ;D........ >>Which reminds me of hiking in Glacier National Park, I was alongside Elizabeth lake and a party of 3 were hiking on the other side early in the morning when all of a sudden one of their members started coughing and gagging like he was about to die....It went on for a few minutes...I still remember being very concerned. When we met up I asked if he was OK and all that had happened was that he had gotten a bug caught in his throat!  :P