Filmed in stark black-and-white and set against a spit-and-sawdust bodybuilding gym in the Northeast of England, Gerard Johnson’s Muscle follows a disaffected, middle-aged call centre worker named Simon (Cavan Clerkin). Feeling unmoored in his life and his marriage, Simon turns to the local gym in an attempt to shore up his physical strength and his sense of self.

It’s here that he meets the charismatic and imposing Terry (Craig Fairbrass, giving a performance of real menace and depth), who offers to be Simon’s personal trainer. But Terry grows increasingly overbearing and emotionally manipulative with his impressionable charge, with glints of racist violence and prison stints in his past that hardly bode well.

Despite its premise, Muscle should not be mistaken for a straightforward macho crime flick, Johnson says. “These types of films are normally very male-centric, and especially with someone like Craig in the film, you’re expecting something. But at its core, it’s a relationship drama.”

For all the talk about ‘toxic masculinity’, what’s especially trenchant about the film is the sympathy it engenders in its portrayal of the confused and wounded Simon, who admires Terry’s machismo even as he grows to suspect that his friend is not who he says he is. Simon begins to physically alter, bulking up and shaving his head, and an attitude change comes with it. “You see it all the time in these gyms,” Johnson explains, “men change the way they walk; but behind all the steroids and muscles and tattoos, there are a lot of very insecure people. A lot of the reason for why they do it is to build a shield of armour for themselves.”

The unforgettable centrepiece of Muscle is a drink-and-drug-fuelled party which Terry throws at Simon’s house. It starts harmlessly enough, but soon descends into a nightmarish, blurred-at-the-edges orgy which Simon can’t fully recollect in the morning. Johnson actually shot these explicit scenes over the course of two days with the permission of a real-life swingers club. “It was a minimal crew, and it was a real party. They were used to us very quickly. It was a very, very intense filming experience,” the director recalls.

Muscle was cut in order to secure a lower certificate in France, and that less explicit version also appeared at the BFI London Film Festival in 2019. The current VOD release, however, is the proper director’s cut. “It’s such a pivotal moment in the film,” Johnson says. “Simon’s gone over to the other side. It’s not that it needs to be gratuitous, but you need to be out of your comfort zone.”

As the mood grows darker, Terry’s more predatory tendencies become clear, in more ways than one. It’s rare to see an abusive relationship play out between two ‘tough guys’ given the way victimhood is usually portrayed on screen; white working-class men are typically seen as perpetrators rather than victims of sexual and psychological abuse.

Visually, the film adheres to a myopic, anxious perspective, putting the audience on the same uncomfortable ground as its protagonist and seeing his rippling fears grow and mutate into rage. Simon views the few women in his life with emasculated fear, and they forever seem to be jeering at him. Whether they actually are jeering or not is beyond the point – it’s Simon’s psyche that’s directing our gaze.

“We’re seeing it a lot nowadays, in what’s going on in the current climate,” Johnson says. “Men are feeling slightly lost, or unsure of where they fit anymore.” It makes perfect sense that, as a result, men like Simon might look to reinforce or reassert their sense of masculinity in the gym. But it’s not all just retrograde, as Johnson points out. “These gyms are like community hubs, and there are lots of wounded men who go there to talk about their problems: their troubled relationships, the jobs they hate. It’s almost like their tribe.”

That tribe becomes almost like an intoxicant for Simon, who is inextricably drawn to the new lifestyle Terry introduces to him even at the expense of his work, marriage, and well-being. A smart, disturbing foray into the unfashionable world of the masculine ego, with real-world questions about what fragments are left behind for working-class men in 2020, Muscle might just be one of the most socially-relevant films of the year.

Muscle is released in cinemas and video on demand 4 December, on digital 18 January and Blu-ray and DVD on 1 February, 2021.