That's something I have always been wondering. Did they do the same exercises athletes do nowadays (like squats and push ups)? It's obvious that everything today is very professional, especially with the growing use of science and technology in sports. But what kind of exercises did Olympians do when nothing like that was around?
The Olympics by the 5th century , or their equivalents since the original shadow of the festival was long banned by Theodosius in the 4th century, this question should be rephrased to around 2000 years ago or earlier at the very least because this was the peak Olympian era.
Even towards the 2nd to 3rd centuries, the Olympics waned in popularity amid corruption, and were certainly not like the Olympics as experienced prior to Roman hegemony.