Thanks for the info Pentaz. Anyway is it possible that i would get big arm muscle gains if i were doing only pull ups?

Pull ups will work your Lat muscles and biceps, thought i guess you cannot expect them being massive from that. Pull up as all self-weight strength exercises are great, even better than bb weight training, but you won't see such an great transformation in biceps, however you will see a change if that's what you're thinking :P

If you heavily do such exercises with self weight, you would train similar to gymnastic competitors so this is how they look:

[img width=700 height=511]http://www.gimnastika-cakovec.hr/admin/upload/filip_thnx.jpg” />
they are muscular and well built but not as nearly muscular as bbers. However their strengths are amazing, as well as coordination and their muscles are well trained to lift their own weight as if it was a paper.