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There's so much sex in the upcoming "Nymphomaniac" that viewers can't help but get sick of it by the end of the movie, one of the film's stars told FOX411.

"When you see it, after awhile you don't react on the sex scenes anymore it becomes as natural human behavior as eating," "Nymphomaniac's" Stellan Skarsgard told FOX411. "I mean one body part entering another body part -- how interesting can it be in the long run? For four hours."

While many European audiences have taken to the sexually explicit nature of the movie, U.S. audiences will get their first glimpse of the Lars von Trier film this Friday.

"Only Lars could do a film called 'Nyphomaniac'," French model and "Nymphomaniac" actress Stacy Martin told FOX411. "The way he describes it was like, 'I'm doing a porno movie but you don't have to have sex.' I'm like, 'Okay'."

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While Martin was immediately accepting of the sexual content in the film, not everyone was ready to give it the green-light. Romania initially banned the film but went on to change their minds.

Maybe that's because there isn't any actual sex between the actors. Although there was plenty of steamy scenes between the porn doubles, Martin revealed.

"For the sex scenes we would do the scene...and have these little black dots on our bodies," Martin explained. "It was all very weird and mechanical and then [they brought] the porn doubles in and they [did] the same thing and actually [had] sex."

Hollywood newcomer Martin said she was excited to do the film but refused to have sex on screen because "having sex on screen is not [her] job."

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But having substitutes perform the sexual acts was okay with Martin.

Another actor who was happy to sign on to the movie was Christian Slater.

"I was certainly happy to see the film in Berlin the first time with an audience that wouldn't be so shocked or overwhelmed with some of the images," "Slater said.

Co-star Skarsgard agreed with Slater and told FOX411 he couldn't understand what all the fuss was about. "The problem is... everybody does it... so what's the big fuss?  "I think it's remnants from when the church had much more influence. I grew up with naked parents around, to me it is nothing."

"Nymphomanciac" comes to theaters in the U.S. Friday, March 21.