I'm only half educated on the actual biology and general goings on in the body. I'm sure you've all watched the All Access on my favourite fighter, Wanderlei Silva. I saw that Wanderlei was tired in his fight with Chuck. I realize that they were both working hard and that it's not unreasonable for them to be tired but listen. I was suspect of his training methods when I saw them. Ross Enamait and countless others preach methodologies to the effect of "train as you compete". His oxygen restrictive training doesn't reflect the environment of a fight. I could see it making him tired faster in training but I don't necessarily buy into the benefits. He maybe teaching his body to work with less oxygen but he isn't increasing his work capacity. Using the example of someone like Sean Sherk, a man that will train intensely for long durations, I can see the obvious benefits. His work capacity is outstanding and he never gets tired. Am I correct in my thinking that simply reducing oxygen intake will not improve ones cardio? I know all about high altitude training but I don't think its the same as breathing through a snorkel. For one, you're inhaling more carbon dioxide with the snorkel.