From Charleze Theron in 'Monster' to Christian Bale in pretty much every film he does, there have been some great examples of actors transforming their bodies for roles in the past.
It clearly requires a tonne of dedication and discipline. But also, for Alexander Skarsgård anyway, a lot of Italian disco pop.
"We were listening to a lot of old-school electronic music from the '80s, and also an Italian disco genre called Italo. It's a whole genre of this cheesy, cool electronic music from the '80s, from Italy. Many times, Italians are singing in English without knowing the words."
To our surprise, it turns out Italo wasn't the only contribution to the 'Northman' star's regime. Intense diet and exercise also had a big enough part to play too. Who knew?
"He ate everything from steak to lamb to chicken, a lot of fish, eggs, quinoa, barley, farro, potatoes, even pasta and a ton of vegetables," said the trainer.
But, of course, the most important question was how did he get his shoulders to look so massive?
"I do movement coaching and I worked with him. An actor can give you 200 emotions, but I can tell him to give more depth in the back, so your rhomboids pop out more. Or rotate forward so your trapezius pops out so you look more animal-like. That's something I can help with.
"And honestly, it's all movement. It's movement and postural manipulation. The way he was carrying himself made them pop. They weren't bigger than anything else."
I mean, they were definitely bigger than most people's shoulders, let's just say that. But it's clear posture has a lot to do with it. So if you want larger trapezius muscles, trying hulking over like a big Viking and you're set.
Filming for Robert Eggers' new Viking epic seemed fairly unforgiving, to say the least. Filmed mostly in a rainy Northern Ireland, even Skarsgård needed a cheat day or two.
"We did it on the weekends because we were isolated. It was during pandemic, so we're stuck in his house in Belfast," said Lygdbäck. "We would have a glass of wine, watch some soccer, and cook for hours. A casserole or steak, fish. Maybe with a nice little starter. It was more about the quantities — I would say that we're overeating and maybe adding a glass of wine."
'The Northman' is currently out in Irish cinemas.