Jake Gyllenhaal has made a career out of suffering for his art, whether it is losing 13kg to portray a shady crime reporter in last year's Nightcrawler, or putting on 28kg and taking punches to the face to play a boxer in the new movie Southpaw.
Speaking to Life about Southpaw, the 34-year-old swears he does not enjoy these painful transformations, even though it was his idea to make his Nightcrawler character look gaunt, which he dropped 16 per cent of his weight to achieve.
"I don't believe in hurting yourself, but I don't think pain is always a bad thing. I think physical pain is part of changing yourself, and pain is part of change," says the actor, furrowing his brow.
"So I wouldn't say I enjoy it, but it's something that I recognise will usually lead to something better and maybe an evolution of yourself in a certain way."
The actor - who in person can be grinning cheekily one minute and brooding intensely the next - has certainly evolved in recent years, leaving behind action blockbusters such as The Day After Tomorrow (2004) and Prince Of Persia: The Sands Of Time (2010) in favour of smaller, edgier films such as Prisoners (2013) and End Of Watch (2012).
He also pushes himself even when it is not for work, volunteering for a gruelling trek through the Icelandic tundra for a 2011 episode of Man Vs Wild, the survivalist television show hosted by Bear Grylls.
The genuine danger he put himself in may have seemed baffling, but the star says he did it for the adventure.
"It's a blessing, the job that I've been given, and it opens up so many experiences. The reason I do it is to not always stay in the same place. It's to learn and grow. Going outside of your physical comfort zone always brings something interesting. And it's the same thing, going to an intimate place that makes you vulnerable and that will grow you.
"It's about looking for situations where you're constantly going to learn about yourself."
The actor brought that same philosophy to his preparations for the boxing movie, which co-stars Rachel McAdams and opens in Singapore tomorrow.
The role meant he had to pass for a championship fighter with the aid of few special effects and no body doubles - even though he had never boxed before.
"I trained twice a day for five months and I was basically driven by the fact that I was afraid I was going to look like an idiot when we got to shooting."
Director Antoine Fuqua (Training Day, 2001) wanted to shoot it like a real televised fight and told Gyllenhaal he was not going to "fake it - we're going to have to see your footwork, no doubles".
Gyllenhaal recalls: "So I figured if I trained twice a day, I could make five months 10 months. And a lot of those hours were spent going 'jab, jab, jab, jab, jab, jab, jab, jab, jab, jab, jab'," he says, punching the air in front of him. "It took me a month to get my jab down."
Subsequently, he took hits to the face and body throughout filming.
This ferocious work ethic runs in the family, says Gyllenhaal, whose sister is 37-year-old Oscar-nominated actress Maggie Gyllenhaal (Crazy Heart, 2009).
"My maternal grandfather was a surgeon - he became a doctor when he was 22, and my grandmother was a paediatrician. They both worked incredibly hard and I think I inherited from my grandfather, in particular, that sense of discipline."
As much as Southpaw is about boxing, it is also about family.
Gyllenhaal says family is paramount to him and his role in the movie, where his character has to fight to regain custody of his daughter, tapped his desire to start his own someday.
"The reason Antoine wanted to make this is not just because of his love of boxing, but also to let young men who become fathers know how this is the most honourable thing they can do with their lives."
He says he picked up a few parenting pointers from Oona Laurence, the 12-year-old who plays his daughter in the film.
"She's an extraordinary actor to begin with, but meeting her, I just fell in love with her," says the actor, who has dated singer Taylor Swift and actress Reese Witherspoon and is reportedly unattached now.
He remembers being confounded by Laurence's wild imagination when she started improvising during a rehearsal, but eventually "I just found myself being guided by this little girl".
"And I thought, 'This is the parentchild relationship. The parent is guided in the same way.'"
The film also resonated with him because of its message about reinvention, with his character forced to change his boxing technique and approach to fighting when his career tanks.
"I love the metaphor. Because life hands you so many different blows, the techniques that brought you so much success all of a sudden don't work anymore.
"And it's those who know how to switch up and fight and how to keep going who really succeed."
Of his own career reinvention, veering off the action-hero track he seemed to be taking with films such as Prince Of Persia, he says: "I think maybe I jumped too early into larger-scale productions - before I understood myself and what I wanted to do.
"I now know more what I think would be really fun to do and fulfilling, and also what I might be better at. I just think you need to know where you fit in and where you can really kill it, you know?"
The course correction seems to be paying off, with Gyllenhaal earning glowing notices for many of his recent films and Southpaw generating talk of a second Oscar nomination for the star, who earned his first for Brokeback Mountain (2005).
Moreover, many fans and critics felt he was robbed when his performance in Nightcrawler was not nominated for an Oscar earlier this year - an oversight that studio boss Harvey Weinstein has vowed to remedy when the time comes to campaign for Southpaw next year.
Asked about the slight, Gyllenhaal says he does not go into any film expecting silverware.
"It's so hard to make a good film that when a movie works, it literally feels like a miracle," he says.
But he admits feeling slightly gratified at the outcry among his fans over the Nightcrawler snub.
"My fans are everything so I don't want to disappoint them. But I kind of like it when they're a little upset," he says impishly.
"It gives them a little more drive and a little more motivation... to be even better fans."
- Southpaw opens in Singapore tomorrow.