Since it looks like this will go unanswered by an actual historian, I'll point out that weightlifting is not a modern invention. The classical Greeks were famous for weight training, and we do have some artifacts from them, but they were dar from the only ones.

This is a good (non academic) overview. If you want an academic's view then pretty much anything by Dr Stephen Miller should interest you.

Did they even do that intentionally? This question seems to be based on the idea that men have been trying to look like body builders since the dawn of civilization. Can anyone comment on that?