In the first Rocky film (1976) there is a scene before the big fight which alternates between Rocky and Apollo Creed’s dressing rooms. We see them taping their hands, sniffing something and then there’s this:
Skip to about the 3 minute mark and you’ll see Apollo’s trainer standing behind him, grasping him around the belly. Another man is in front of Apollo doing… something. Checking for a hernia? What’s going on there? And while we’re at it, what substance are Rocky and Apollo both sniffing and why?
I don’t think drug testing had hit pro boxing yet. Some local athletic commissions may have required it. There is no overall governing body in boxing that could enforce something like that but it began to be specified in when boxers contracted to fight.