By Conor White

Thor Björnsson may hold the title of "World's Strongest Man," but even he struggled with filming the final season of HBO's smash hit "Game of Thrones."

"This was the hardest season that I've filmed with 'Game of Thrones'," Bjornsson told Cheddar Wednesday. "Physically and mentally, it took its toll ー it was very long hours some days for me. I can't go into more details, but it was very hard."

"Game of Thrones" is slated to return for its eighth and final season in April. Although it only consists of six episodes, each installment is reportedly over an hour ー which means a beyond-demanding production season.

Björnsson, who plays "The Mountain," a.k.a. Ser Gregor Clegane, is used to overcoming challenges: he broke the the Elephant Bar deadlift world record by lifting 1,041 pounds. And Wednesday night, he'll be testing his strength against Krazy Glue in a contest in New York City that will stream live on Facebook.

His training never stops ー not even when the star is inhabiting one of the most terrifying roles on television.

"I have to eat 10,000 calories a day," Bjornsson said. "It's a lot of steak and rice. Six times a day, steak and rice; it's a lot of food."

Whether he's competing in a strength contest or appearing in a television series, Björnsson says his focus is the same.

"You know the whole world is going to watch, so you want to perform well," Björnsson explained.

"You do whatever you can to be 100 percent on the day," he added.

So, how does "Game of Thrones" end, anyway?

"I would love to be able to share that with you," Björnsson teased.

For full interview click here.