It’s the early days of really crap camera film that needed about a minute of exposure time. She probably could lift three men at once - if she found three horse jockeys, that might be less than 120 kg - but couldn’t hold the pose completely motionless for the time needed to take the picture. Hence the ‘carefully staged’ photo.
There’s no strain in any of those muscles. My guess is that black background is designed to hide whatever contraption is supporting the men.
It’s the early days of really crap camera film that needed about a minute of exposure time. She probably could lift three men at once - if she found three horse jockeys, that might be less than 120 kg - but couldn’t hold the pose completely motionless for the time needed to take the picture. Hence the ‘carefully staged’ photo.