I've always assumed there are biological reasons for it - children just seem to have huge amounts of energy and very fast metabolisms, in general. I suppose there's also the fact that people become more unfit, which makes running more uncomfortable, which leads them to run less, which makes them become less fit still, and so on ad nauseum. Anyway, I enjoyed the podcast, especially the connection between running and mental control. I don't tend to find running a euphoric experience (not after it, and certainly not during) but I do become very calm and confident afterward.
Thanks, I'm glad yo enjoyed it. I liked the part about "mental control" too. Cliff is right on the money there. So much of what I am capable of running wise, and otherwise, has to do with whether or not I'm in the right frame of mind. Much like the children's story about the Little Engine That Could. If you think you can't... you won't. If you think you can... you will. Either way, you're right. Happy trails.