Running will make your feet to float. It's much easier to take down a runner than to take down a non-runner. It will reduce your ability to resist any throw.
In the ancient time, the "low stand wide step fast walking - upper leg to be parallel to the ground" was used to replace the running training.
http://img26.imageshack.us/img26/3669/lowwalk.jpg
Today, people may have ignored this issue.
What's your thought?