I have just read the above article by Amby Burfoot, and had to say that my 5 year old son agrees!
I am a beginner runner, and sometimes take him out for a warm-up or warm-down lap of the block, figuring he would enjoy it (he does), and it would be good for him. The only problem was that he would sprint off, trying to beat me, and then walk for a while. One annoyed Daddy!
.. but according to this article, he was right all along... I shall be taking more training advice from him in the future!