David Blaine twists his arm for 360 degrees in an seemingly impossible manner.
How does he do it? Does he have superpowers? Or just insanely flexible arms?
No. This is simply a clever optical illusion.
The secret lies in the starting position of Blaine's hand. Because he is wearing long sleeves, we are unable to see the real position of his hand and therefore assume that it's in the position that seems the most natural to us. However, his arm is already twisted when he starts. All he has to do is simply untwist the arm and act as if it hurts like hell.
Here is a video explanation for easier understanding.