Hafþór Júlíus Björnsson is really, really strong. In addition to playing Ser Gregor Clegane, aka "The Mountain That Rides," on HBO's Game of Thrones, Björnsson also accomplishes absolutely ridiculous feats of strength on a regular basis. He was named the strongest man in Europe last year, and before that, he broke an ancient (and probably fictional) ancient Viking record when he carried a massive tree on his back.

You might assume, then, that Björnsson would prove to be a formidable arm-wrestler — and against any regular Joe, you would be right. But when his opponent is World Arm-Wrestling League champion Devon Larratt, well, let's just say Björnsson should stick to lifting heavy objects.

You can watch the video of the epic arm duel at the bottom of this post. Both men feature some comically large biceps, sure, but overall, Björnsson is nearly 200 pounds heavier than his opponent. You might think that gives him an advantage, but you would be wrong. Larratt's performance shows that it's not just strength that matters in arm-wrestling, it's also technique.

Poor, poor Mountain. He can defeat nearly any opponent on Game of Thrones, cleave a horse in two and carry a tree, but he can't beat one guy with superhuman biceps. Looks like he still has a little more training to do if we wants to be the strongest at everything — which, at this point, seems like a goal that might just be obtainable.

To see what other Game of Thrones actors have been up to, you can read about a recent Kit Harington sighting that may point to the return of Jon Snow or read more about how Emilia Clarke really feels about sex scenes on TV.

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