For years the three Staples of chest development I have known have been upper pecs, middle pecs, and lower pecs. There are a lot of posts about inner and outer oec development.. and even a lot of information from classic bodybuilders such as Schwarzenegger. My question is.. can these actually be trained and if so should they even be a focus? I do a three day workout a week so my exercises are the big compound movements without a lot of extra isolation exercises like flyes or cable crossovers. I thought I also remember in some medical journals that there's no such thing as outer or inner pecs.. outer pecs are really part of your lower pecs and inner pecs are part of the middle.
If these are necessary to train, how can I tell if I am lacking in one? I know too much development in lower pecs look like breasts, and too much in middle makes your chest jut out.. but how can I tell if I'm missing inner or outer?