Wiktionary
pump iron
vb. (context idiomatic English) To lift weights; to engage in weight or strength training.
Usage examples of "pump iron".
The guard encampment, just outside the city in what had been a Jewish settlement until less than two weeks before, had its own high-tech gymnasium, and the men were 'encouraged' to pump iron until their exposed skin looked as taut as a drumhead.
It's a lot easier to get a chimp in roller skates than it is to get him to pump iron -- hence, most of the data on chimp strength is anecdotal and decidedly unscientific.
He looked the sort of small man whose touchiness over his size drove him to pump iron and collect guns.
I had access to a gym since I worked and lived in a wrestling school, so I started to pump iron and do steroids.