This is what’s known as a physique film, and it is vintage gay porn. Actual gay pornography was illegal in the 50s, so people created short films like these that existed in a legal gray area - the (paper thin) excuse is that they are about bodybuilding and fitness. No sex happens in physique films, nor any full-frontal nudity, just a lot of the kind of thing you can see in these gifs. The film reels would be ordered by people through the mail (via physique magazines - which were magazines of homoerotic photography along the same lines as these films) and would not have been screened in theatres. Since they were not a product of the movie studio system, physique films were not subject to the Hays Code, but that did not mean they weren’t extremely legally dubious. Physique films and magazines were dangerous to make, distribute, and consume because of obscenity laws, and most of the important figures in the industry were arrested at least once.