For some examples of ab armor Barbarians on Netflix Monty Python Life of Brian Roman Empire on Netflix Additionally many depictions of Greek hoplites also have ab armor most notable Spartan.
Actual Roman armor, I believe, didn't have this.
Not the majority, no, but the 'muscle cuirass' with all them abs is definitely A Thing for the Greeks and Romans. The Medievals also got into the action - the consequences of making plate and being Classical fanboys. More can always be said about the muscle cuirass if anyone would like to contribute their knowledge; for the meantime, here are some previous posts that deal with abs-in-metal: