5
Low reps builds bulky muscle, high reps for toning muscle
“Confusing your body” and “shocking your muscles”
To be fair to Arnold, this was the 70s and 80s when exercise science was quite elementary
Its insane how many people still believe this despite literally everyone who knows anything about fitness telling them it's wrong
Not saying he's right or that people should still follow his training. I'm saying that he didn't have the proper information available at the time.