An active Marine who trained a lot once told me, "Whenever I do my personal best at bench press my running is way off, and whenever I am at my best at running my bench press suffers".
Alan Page was a 260 pound defensive tackle for the Minnesota Vikings. Toward end of his career he had trained for and completed a marathon – the first active NFL player to do so. He lost a significant amount of muscle; so much so that he switched position to linebacker at 225 pounds. When you run great distances carting around more muscle is demanding.