Jake Gyllenhaal put on 20kg of muscle to play Billy Hope in the film Southpaw. Photo / AP
Six years ago, Arin Babaian was given the opportunity to travel around the world indefinitely with Channing Tatum. There were advantages and drawbacks to this. On the downside, it would mean abandoning his personal training business, which he had only just set up in the affluent, and fitness-crazed, Californian beachside city of Santa Monica. But on the upside, it would mean travelling around the world indefinitely with Channing Tatum.
The two men met a year earlier, when Babaian was called in by the production company Spyglass Entertainment to help the then largely unknown Tatum beef up for the lead role in its summer action movie G.I. Joe: The Rise of Cobra.
The film was horrendous, but Tatum and Babaian hit it off and vowed to work together on whatever the actor did next. At that stage, neither had any inkling that Tatum would become "the most exciting and versatile new leading man in Hollywood", but he had a couple of projects lined up - a Nicholas Sparks romance, a supporting role in a Vince Vaughn comedy - and wanted to look his best in them.
Babaian mulled things over, bid a temporary, anguished goodbye to his fledgling business, and decided to go along for the ride.
It's possible you hadn't heard of Babaian before reading this, but he is one of a small group of personal trainers to the stars responsible for perhaps the most significant change in the way we view leading men since the decline of the studio system more than 40 years ago.
If you've been to the cinema even once in the past couple of years, you'll probably have noticed that actors are getting, for want of a better word, ripped. In Antoine Fuqua's Southpaw, released this week, Jake Gyllenhaal is the latest leading man to muscle in, having piled on 20kg of pure muscle to play a professional boxer.
When the first photograph from the film emerged last year, Gyllenhaal's swollen, vein-riddled physique sold the unexpected casting decision in a moment.
Nothing says commitment like doing 2000 sit-ups every day for five months.
But this trend isn't apparent only in conspicuous Oscar and Bafta bait, films designed to appeal to voters who have prized physically transformative roles since Robert De Niro gained 9kg of muscle, and a further 25kg of flab, for Martin Scorsese's Raging Bull, and won the 1981 Academy Award for Best Actor for his considerable trouble. It's there, too, in the blockbusters, the romcoms, the superhero movies, the family-friendly capers.
Cinemagoers who saw Marvel's Guardians of the Galaxy last summer were treated to the sight of Chris Pratt showing off the kind of torso that wouldn't look out of place in a Tom of Finland print. This northern summer, he did the same in Jurassic World, albeit with a vest stretched tightly over the top.
Pratt's roles - a wisecracking space pilot and a wisecracking dinosaur trainer - don't exactly demand that kind of marble-hewn physique, and until recently it would have been easy to picture him playing both at a fraction of his current size.
Ten years ago, leading men in popular movies looked like Johnny Depp, Hayden Christensen and Elijah Wood. Physical fitness was rarely just a matter of looking good: when Tobey Maguire bulked up for Spider-Man, the grand unveiling of his sculpted chest was played for laughs, and Christian Bale's obsessively toned abs, pecs and delts in American Psycho were symptoms of a poisoned mind.
Exactly what has changed? Talking on the telephone from Los Angeles, Babaian, a 43-year-old New Yorker whose accent has been softened by years of West Coast living, has a few ideas. The first is that actors are increasingly using personal training as a way of immersing themselves in a role that stops short of the obsessive mania of Method.
"It's not necessarily about being in the best shape of your life, but working out who you're trying to become," he says. "We'll spend a lot of time at the start discussing the character and tailoring the exercises to get into their head space as well as their body."
When Babaian trained Tatum to play a stripper in Magic Mike (2012), the exercises were geared towards shaping his body into a "golden ratio" physique. Shoulder presses and sit-ups helped to mould his upper body into the same kind of harmonious V-shape Michelangelo used in his nudes on the ceiling of the Sistine Chapel.
But for Foxcatcher (2014), in which he played an Olympic wrestler, his regime involved dumbbells, dead-lifts, endless holds and throws.
In training Joseph Gordon-Levitt for the comic drama Don Jon (2013), in which he played a vain New Jersey gym bunny, the two did push-ups and stomach crunches in character, egging each other on throughout the workout.
Last year, while preparing for Gordon-Levitt's forthcoming film The Walk, in which he plays the French tightrope artist Philippe Petit, Babaian stood him on a gym ball and made him catch beanbags.
"The training isn't separate from rehearsal," Babaian says, sounding a little stung, when I ask how much time this takes away from learning lines. "It is rehearsal."
In that respect, the toned bodies of the 2010s couldn't be further removed from the Muscle Beach look popularised by the likes of Sylvester Stallone and Arnold Schwarzenegger in the eighties. Back then, an actor's body was their brand. Now, it's just another tool in their arsenal.
But however keen some actors are to embrace rigorous physical fitness, modern audiences seem to be with them every step of the way, and this is where the revolutionary part comes in. On the Jurassic World publicity tour, Chris Pratt tried to articulate what was going on, with limited success.
"I think it's appalling that for a long time only women were objectified, but I think if we really want to advocate for equality, it's important to even things out," he told Radio 4's Front Row. "Not objectify women less, but objectify men just as often ... There are a lot of women who got careers out of it, and I'm using it to my advantage. And at the end of the day, our bodies are objects."
Pratt was widely criticised for his remarks, presumably by people who have yet to twig that going to the cinema entails little more than sitting in a dark room, staring at beautiful people who can't see you. Cinema and objectification can't be pulled apart: what Pratt was getting at was that the ways in which men and women are looked at by the camera is changing.
In a 1973 essay, Visual Pleasure and Narrative Cinema, the film theorist Laura Mulvey brilliantly nailed down the difference. What usually matters about female characters is how they make male characters feel, and the camera's gaze almost always replicates that relationship between them and us, turning them into objects for us to look at and appraise coolly - or, just as often, hotly - from a distance.
But the leading men are the ones we're normally supposed to identify with directly: Mulvey likens the relationship to a child recognising himself in the mirror and being excited at seeing himself somewhere else - with an added rush of pleasure at his double's apparently central role in the reflected landscape.
Except when the camera lingers on Pratt's body in Guardians of the Galaxy, or Henry Cavill's in Man of Steel, or the gym-toned lead actors in any number of other recent hit films, that isn't what we're being invited to think at all, despite the toddler-like gurgles of delight it might provoke.
In Magic Mike XXL, when Tatum starts grinding against his workbench to the strains of Pony by Ginuwine, the scene is shot and staged in a way that puts Tatum's body on display purely for the pleasure of looking at it - except that the uneasy power dynamic that raised a red flag for Mulvey, with the gazed-at character reduced to a passive pin-up, is turned on its head. Like all the dance numbers in the film - and all the ab and pec flashing, come to that - it's a performance in which Tatum is happily complicit.
This, I suspect, is what Pratt was driving at in his Radio 4 interview, and what Babaian articulates with pinpoint accuracy.
"Women have been looked at in this way in films for generations, and I think what's going on at the moment is kind of an apology for that," he says. "It means there's a kind of role reversal taking place in the audience. It's as simple as making it possible to look at a male actor whom you find physically attractive and say, 'I like that'."
It's a small shift in viewpoint, perhaps - but it feels like a seismic one. The old studio system that ensured actors and actresses kept playing the roles audiences expected them to is gone, but the rules it established to govern how we should look at them are more or less still in force. But when a major film ignores them completely - as Mad Max: Fury Road did when it put Charlize Theron in the driving seat, for example, or Magic Mike XXL does in its numerous dance scenes - you can feel your eyes adjusting to the new perspective. Tatum's six-pack is changing cinema, and by ogling, you, too, can play your part.
