Sverrir Gudnason ate seven meals a day to train for 'Borg/ McEnroe'.
Sverrir Gudnason
The 39-year-old actor stars as legendary Swedish tennis player Bjorn Borg in the forthcoming film, and was on a "strict" training programme to get in shape for the role.
He said: "I had to grow my hair, I had to train a lot, both in tennis and building muscle. I ate seven meals a day.
"I was on a strict boot camp programme for six to eight months."
The motion picture tells the story of Borg's rivalry with US tennis player John McEnroe (Shia LaBeouf), who he faced off against in the 1980 Wimbledon tennis final, and Sverrir admitted he "kept a distance" from co-star Shia during filming.
He said: "He's a brilliant actor, one of the best I've ever worked with. He uses his energy in such a good way, and he's very devoted to the part.
"We had a mutual respect on set and kept a distance; I tried to keep the magic between us a bit."
The pair had to recreate the exact famous Wimbledon final between Borg and McEnroe, including replicating each point.
Sverrir said: "We played a lot of tennis: we had to memorise all those points together. If you look at the match in the film you can find every point in the real match. We had to learn them."
The Swedish star also had to recreate many of Borg's rituals, and admitted he once had some superstitions in real life, including eating a yoghurt at exactly the same time of the day before going on stage.
Speaking to TimeOut London magazine, he added: "Every day I had to drink the same brand of drink, eat the same yoghurt at the same time and plan my day the same leading up to the show.
"One day I just said, 'I'm gonna try something else, I'm going to break the spell.'
"So I did it differently and the show worked out. Now I'm free!"
Tagged in Shia LaBeouf John McEnroe