Despicable Me - Why does going to the movies make you so tired?

I just got home from seeing Despicable Me. It was actually pretty hilarious!
What I find really weird about watching movies at the theatre is that even though you were sitting down the whole time without moving, you feel exhausted when you walk out.
I’m not a movie expert or reviewer or anything, this is only because my parents were off for 2 weeks and they wanted to go out a little before work starts again.



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