We've all seen guys with big arms at a local gym (or we ARE one of them ) There's at least one or two of them in every gym. You know, arms that aren't huge, but still big and impressive, giving observers the immediate impression that their owner is into strength-related sports. There are at least two in the gym I go to. How could they have achieved that? What I've noticed, they don't spend much (if any) time working on their legs. Mostly chest/shoulders/bis/tris/back. I work my arms 3 times a week following HST principles, but no one could ever refer to me as the one having big arms. I can think of at least these reasons: (1) they do more volume than me. (2) lack of proper leg training leaves more resources for upper body growth (3) better genetics (4) something else?