This is a little out of the ordinary but here's one objective measure, resting heart rate from 63 to 45bpm after only 4 weeks of a 10 week program.
The Wim Hof Method is involves exposure to cold, meditation, stretching and breathing exercises. About an hour a day at most.
I instantly increased my max pushups from 30 to 45 after five minutes of breathing. I can now do 68 pushups while holding my breath after just four weeks in the course. My wife went from 10 to 22 after five minutes.
My goal is to ski with only shorts at minus 15 this winter. I might SUP the bow on a cold day too. While these are fun stunts, I am really benefiting already in terms of sleep, insanely better mood and better concentration.
I am pretty sure the breathing technique alone delays the onset of lactic acid build up. Would be curious to see if a hockey shift would go easier after doing this right before hopping over the boards.
http://www.wimhofmethod.com/
The recent documentary on the guy.
http://www.vice.com/en_ca/video/iceman
Laird Hamilton on the Power of Breathing to Succeed with Lewis Howes
https://www.youtube.com/watch?v=sTU3reidiWY
He trained people for two days and then took them up Kilamanjaro in a 48 hours without anyone becoming ill for a group world record:
http://www.reuters.com/article/2014/...0IK29Y20141031
Then he did it again last year with another group in 32 hours:
http://www.icemanwimhof.com/wim-hof-...ithin-32-hours