This is because phenomenologically, watching the movie reminded me of some crazy home fitness contraption I read about last week that looks like a cross between a torture device and an amusement park ride that basically whirls and shakes and drills you for ten minutes until every muscle is sore. I think Madonna will soon use it.
The movie was relentless. Its makers did stuff with light and speed that I've not yet seen in a horror flick (though I'm no expert--in fact, I don't even like the genre). I wouldn't be surprised to learn of the film inducing siezures or otherwise inflicting bodily harm. This morning my eyes are swollen, my jaw is sore, and my knee hurts.
And I loved it.