I made a thread on this a while ago too, it's an insane exercise. When his shirt is off, you can see his neck muscles bulge and contract as he does it. He's got muscles on his muscles. I recommend trying the exercise yourself, it's incredibly hard.
OR 1. http://sports.kz/upload/2015-10/5620b1a87f8ca.jpg 2. https://pbs.twimg.com/media/Crhr2byUEAQ4Fyd.jpg 3. https://i.ytimg.com/vi/sLSAN815RAA/maxresdefault.jpg