Energy Vampires

I spent two days last week as staff at a Cub Scout Daycamp. I spent ten hours a day surrounded by six to twelve year old boys who were incredibly excited and frenzied. The kids were very keyed up and ran from the activities to the games without pause. They only slowed down if food was available. They refueled and then were off and running again. I was busy from son up to son down.
Upi Dupi, I was so tired by the end of the second day; I could barely keep my eyes open. It only took me four days but I think I’m finally recovered.
There must be some correlation between the energy level of the kids and the fatigue felt by the grown ups. I’m sure I’m not the only one to notice this strange connection. How is this energy transference possible? Is there only so much energy available out there and the kids suck it all up or do they drain the vitality from the adults around them. I’m not sure how the little energy vampires do it, but they can really suck the life out of you.