"Of course body building and competitive running are incompatible"
Depends on your weight class. Depends on what show you do. Depends on what you mean by competitive.
Bantamweight Bodybuilding is 143lbs. I've seen guys who run 16:00 5ks who look like they could place or win a Bantamweight title if they got lean. No, distance runners are not lean enough. Your average 5'8, 150lb distance runner would likely have to cut to 135-40 to get that ripped shredded look (ie: sub 5% bodyweight).
Alan