This has been mentioned several times over the past two days. He addressed it years ago - he gets a lot of sweat in his
eyes, and it causes the pads in his helmet to stick to his face. He does it to separate the pads from his skin when they stick.
Twitter just thought I should address the head shakes during the game lol . During the game I sweat and it causes my face to be wet. While my sweat drys on my face it causes my pads on the inside of my helmet to stick to my cheeks. If I had a head injury I would address it.