I AM WATCHING A VIDEO. In it, one man—handsome and extremely muscular, with bronzed, hairless skin—lies splayed on a hotel bed. He wears only white briefs. At the foot of the bed stands another man. He gazes at the reclining figure and slowly undresses—the video is getting racy now. Viewed from behind, he peels off the top half of his dark blue tracksuit to uncover the sculpted ridges of his back. He turns a little, revealing the vast slopes of his smooth, muscled chest to the camera. If I fast forward twenty minutes or so, these buxom, oil-slicked men will be caught in medias res, grinning ecstatically as they embrace.

I have buried the lede. As closely as it apes it, the film in question is not gay porn, the men depicted not porn performers—or, at least, the film is not intended to be pornographic. No, it’s a different kind of fare: 1977’s Pumping Iron, a documentary that follows, among others, the professional and strictly heterosexual bodybuilders Franco Columbu and Arnold Schwarzenegger as they prepare to battle for the top spot at the 1975 Mr. Olympia, a bodybuilding competition hosted by the International Federation of Bodybuilding and Fitness (IFBB).

Unlike other, explicitly gay fodder, Pumping Iron enjoyed considerable box office success and critical acclaim upon its U.S. release. Even at a moment in history when American culture was, broadly speaking, profoundly suspicious of homosexuality—and even bodybuilding as a pastime—reviewers lauded the film for encouraging its audience to gaze desirously at the awe-inspiring, seemingly monstrous, bodies of its male subjects. Louise Sweet, writing for The Monthly Film Bulletin, commended the film, and Schwarzenegger in particular, for managing to inspire “envy rather than disgust at ostentatious musculature.” In the Washington Post, Gary Arnold wryly noted that Schwarzenegger’s undeniable charm and heroic build were sufficient to make “all of us in rotten shape . . . feel his very presence as a constant rebuke.” Though never explicitly stated, both critics implied a male viewer looking enviously and, accordingly, covetously at the rippling physiques of the film’s stars.

Read in this way, Pumping Iron represents a puzzling contradiction within professional men’s bodybuilding. Namely, while homoeroticism is on full display—its aesthetics, its sustained assessment and idealization of the male form—bodybuilding is routinely presented as the very apex of male heterosexuality: masculinity dialed up to eleven in the hulking, bulging, rock-hard bodies of the professional male bodybuilder. In Pumping Iron, interspersed among the erotic close-ups of flexed muscle and male-on-male tenderness, Schwarzenegger shows off for a group of cooing women at a photoshoot and, later, compares the sensation of lifting weights and pumping his muscles to “having sex with a woman.” In other words, while straightness is front-and-center in the world of bodybuilding, homosexuality is everywhere and nowhere to be seen.

Bodybuilding was not always considered a serious sport. While early adherents like Eugen Sandow achieved fame and notoriety for their spectacularly large physiques, the sport was considered, at best, unusual and, frequently, repugnant for most of the twentieth century—in large part because of its perceived relationship to homosexuality. Indeed, Sandow himself first rose to prominence not as a sportsman but by exhibiting himself as a kind of one-man freak show, demonstrating his supernatural strength and hyperbolic physique to awe-struck Victorian audiences in the late 1890s.

In the decades following World War II, however, bodybuilding underwent a period of deliberate reinvention. The sociologist Ruud Stokvis contends that an abundance of food and increasingly sedentary lifestyles led to rising concerns about the physical health of the population and, in turn, an increasing interest in fitness. With a newfound emphasis on the outwardly “healthy” body, bodybuilding as a pursuit began to accrue some esteem, signifying the superlative health of its practitioners. The newfound respectability of bodybuilding was largely achieved, however, by two individuals: Joe and Ben Weider, two brothers from Canada who founded the IFBB in 1946 with the intent of crafting a demand and reputation for the sport. They worked tirelessly to promote and expand their empire, which by the 1970s comprised, among others, the IFBB, Weider Nutrition, and a smattering of fitness magazines, including what would become Flex and Muscle & Fitness. But the Weiders’ biggest victory was, perhaps, their discovery and patronage of a young Arnold Schwarzenegger, whom they brought over to the United States to train in 1968. Years before The Terminator, Pumping Iron brought Schwarzenegger—and bodybuilding—into the mainstream.