The movies were on tv constantly during my childhood, and now they're all available on DVD.
I noticed something interesting: in all of the Tarzan movies featuring the adolescent Boy, and in all but one of the Bomba movies, Johnny gets tied up.
Did the directors have a bondage fetish?
Or is it a matter of maximizing beefcake?
Johnny begins to get an impressive physique in the last 3 Tarzan movies, which are terrible. Maureen O'Sullivan refused to do them, so Jane was recast with Brenda Joyce.
The Bomba movies are even worse: endlessly recycled stock footage of African animals, and an endlessly recycled plot about Bomba falling in love with a visiting colonial administrator's daughter while fighting poachers or insurrectionists.
How can you get audiences to fork over money to see such stuff?
Easy: show some pecs and biceps, and maybe a loincloth-bulge now and then.
So you add a few scenes of Johnny asleep, or else unconscious after falling out of a tree. The camera zooms in for a close up of his face, shoulders, chest, stomach, and loincloth. Then it starts over again. Before we're done, we've been staring at Johnny's body for five minutes.
But sleeping/unconscious shots show the muscles at rest. Audiences want big, bulging, flexing muscles. Fight scenes with bad guys or wild animals cause bulges, and sometimes the loincloth rides up to reveal the underwear beneath, but there's too much moving around for a serious gawk at Johnny's body.
Idea: why not have Boy/Bomba tied up, threatened by poachers or about to be sacrificed by an evil cult or something? That way he can strain against the bonds, flexing his muscles, but he's not moving. The camera can zoom in, and audiences can stare as he struggles for five minutes.