As the growth hormone levels increase, differences in body sides' responsiveness and composition becomes more aparrent. Back in the day, you'd have Arnold's right bicep a little bigger and more split than his left.  Today, that difference would be exaggerated from the GH and more plain ol size.  We see jay's legs different, Dex & COleman's arm differences.  Their muscle bellies & cells are not distributed perfectly. WHen you chemically push them to the limit, this will happen.