Somebody tell me where the energy of tiny, little, 5 year old kids are stored?

I spent the day with 15 kindergarten kids. I wasn't even anywhere near as energetic and active as they were, but the second i stepped through my front door, i found my way to my bed and crashed for 3 hours.

Ok, that was a lie. I tried to fight fatigue, actually. I tried not to fall asleep... exhaustion still won.

Intense.

My 5 year old? He went out for a walk with my mom and my sister. He rode a horse. Walked back home. We went out for dinner. Played with new toys. Now, he's still playing and watching a DVD and singing and dancing with the songs as i prepare the water for his bath.
He's been up since 7am.

I'll bet he snores tonight.