Do not agree with the bolded part. Do agree with the other part though. Stamina isn't stamina. There are different types. A marathon runner would gas within minutes of being in a MMA cage. I'm not saying doing triathlons doesn't help at all with cardio but if the Diaz brothers conditioning program consisted primarily of trithlons they would gas quite easily and quickly.
This isn't something I've just come up with . I buy Fighters Only magazine every month and there was an article in the training session about conditioning. The dude said that the only thing long distance running is good for is long distance running.
I'm not here to say running, biking, and swimming give you great MMA cardio. And no one here said that is all Nick does.
But he has said that he doesn't do a lot of the explosive training that a guy like GSP does or many other MMA fighters. He says that is a better way in hurting yourself in training by doing short explosive workouts. Notice how the Diaz brother rarely ever have to pull out with injury. They keep healthy while training or they fight through it. Same can't be said for a lot of fighters who are "hurt" every year.
Sure there are MMA fighters who bike, swim, and run. Probably none on teh level of the Diaz brothers who said if they were to choose between MMA and those sort of races that they would choose triathlons and stuff like that. Either way the Diaz brothers have some of the best cardio in all of MMA. So the abundance of running and biking they do must be quite helpful in MMA cardio. They spar a lot too.
I have never seen them with ropes or doing weird shit that many MMA fighters do. Yet they don't gas...ever.
There has to be a correlation. No matter what they do, it can be said that they both have great work ethic and love for martial arts. They make sure they are on weight every time and they make sure they can go the full distance if they have too. That can't be said for a lot of fighters who routinely gas at the end of fights with their big old muscles and high tech training.