Um...that definitely sounds way more like porn star moaning and way less like mountain climbing grunting. Go ahead, listen for yourself.
So, did this sound engineer just do this as some sort of twisted, Fight Club-style joke? Or did he just Google "grunting" and wind up with this not-so-convincing sound track? And most importantly, why did the adult filming this think that it was ok to leave that little girl in the room?
We may never know the answers to any of these questions, but they're all worth asking.