all the information in my paragraph (very well explained by other posters since) is correct via recent published work have just taken my exams on it and am willing to go into more detail if someone wants to know!
oh to person who wants to build arms more i take it you mean forearms in which case get one of those squeeze apparatus (grip flex) and just sqeeze it all day its good lol i do it!
http://images.jupiterimages.com/comm...3/23380385.jpg