While in the Marines, we used to circuit train. We would run about a 4-6 mile circuit and stop every few hundred yards to perform an exercise.
If you read "Art of Expressing the Human Body" it details BL's workouts. After it was all said and done, he basically realized that he caould get the same results from circuit training as he did with his previous (more traditional) workout. He would work his bicepts and then immediately work a different part of his body like his calves. This forces his heart to make his blood supply go from his arms down to his legs. And that increased his cardio endurance a well.