Aerobic Capacity is the foundation for endurance of any sort.
It's not the ability to run all day, that's a combination of qualities, but without it you'll blow up fast.
By decreasing your resting heart rate, increasing your anaerobic threshold, widening your aerobic window and improving your recovery rate between bouts of high end sprinting, you'll not only run all day but you'll be running over the grass well after your opponent has been broken.
The AEROBIC CAPACITY LEVEL 2 training manual is a 4 day a week program that builds on level 1. It progresses to more intensity based training methods designed to take you to another level again.
By the end of the 4 weeks you should have dropped your resting heart rate by another 2 - 4 beats improved your recovery heart rate and improved your result for the timed/distance run.