I'm not sure why MMA fans think that just anyone can develop world class cardio. It's just like punching power or a chin or speed, there's a huge genetic component. Some guys just have a major advantage. Nick Diaz could come off of a six month Vegas bender and still have better cardio than 95% of MMA fighters. Just like Roy Nelson's fat ass can roll out of a buffet and hit like a Mack truck and take a baseball bat across the jaw like nothing.