Too many machines and cables instead of good core dumbbell / barbell excersizes.
Proof in pics that he did that and that it made a difference?
Sergio's arms were big, but he had horrible shape to them.
Nah, the shape was good it was a lack of separation and refinement in a lot of pics, and the fact that there aren't a lot of pics out there taken when he was in peak shape. Most out there are well after or before that.