'Game of Thrones' season 6 cast news, spoilers & update: star Hafthor Bjornsson sets new keg-tossing world record

Hafthor Bjornsson is known to TV viewers as the mighty Gregor "The Mountain" Clegane in HBO's "Game of Thrones," but there is definitely more to his hulking, muscular physique than just his intimidating stance. In fact, Bjornsson is a former basketball player who turned to the Strongman competitions after a knee injury prevented him from pursuing basketball.

The 27-year-old is the title holder of 2014 Europe's Strongest Man, has held the title of Iceland's Strongest Man since 2011, and was named Iceland's Strongest Viking in 2010, 2011, and 2012.

More recently, Bjornsson set a new world record by tossing a 33-pound keg over 23 feet in the air, IGN reports.

"It was easy!" Bjornsson said of the feat, in which he broke his own record high. "I could have broken the roof. It was amazing to do this in front of the great crowd. Bring on Europe's Strongest Man."

The professional strongman also managed to toss a 56-pound kettlebell to 19 feet up in th air using just one arm during the Arnold Sports Festival in March. He also broke a 1000-year old weightlifting record in February.

The actor told The Hollywood Reporter that because of his size, he does all of his "Game of Thrones" stunts himself, sharing as he laughed, "How are you going to find a guy of my size and build to be my stunt double? No, I did this all myself."

The 6'9" Icelander also looked back at his audition, saying, "I have to admit I was a bit nervous. I had no clue as to what I was going up against, but then it went really well. We read dialogue from the scenes, but then they wanted me to show them if I was fast enough for the fight scene."

"They were actually surprised at how fast I was, but I am naturally fast and on top of that I have practiced sports where you have to be very agile — and I think most realize I am strong," he admitted.

The actor shared that he had to undergo training before filming the fight between Oberon and The Mountain. He told the New York Post, "I had intense training with the [show’s] sword master, C.C. Smiff, who is also a fantastic dancer, by the way. That was very difficult. We were working from early morning until evening for several weeks, but as you can see, like in the fight scene, all that hard work really paid off."

"Game of Thrones" returns for its sixth season in April 2016.