I think, and if anyone knows more please correct me, that the best way to run is to do sprints. I like to sprint a block, walk half, jog half, then sprint another block. When you look at the Olympic sprinters they've got muscle vs. marathoners who are leaner.
Exactly. I usually post this in comparison:
If you do larger amounts of distance running, it will do pretty much nothing good for building muscle, as the body has zero reason to hold on to any muscle beyond that which is essential for long-term aerobic work. I've challenged people in the past to show me pictures of muscular individuals who engage in long-distance (or long-on-time) regular aerobic work, and so far, the challenge has gone without anyone giving a good example
Being able to run 30 miles won't do any more to build muscle than if you were to curl a soup can for 3 hours straight every few days, so running = bad for trying to gain lean mass. A little bit here and there is one thing, but regular long-term cardio work is counterproductive to trying to really add on mass. The body typically goes to town on cannibalizing precious muscle tissue for long-term aerobic training and doesn't do anything to rebuild it with such training, so unless someone truly loves running for the sake of running, it is completely non-essential for any program where someone wants to gain lean mass. Of course, running has its own benefits, but it's a matter of deciding whether you want to accellerate your progress for gaining lean mass, or, keep up the additional cardio work at the chance that it may hinder your gains.
One day a week of running for an hour won't ruin progress for building some size, but at the same time, it sure won't help you gain any lean mass, and you may end up having to eat more to make up for the caloric deficit from doing longer distance running so as to not have it affect your mass gaining negatively.