I was born missing my Pec. major on my left side. When I lift all the muscles on my side compensates for the missing muscle. It's a rare muscle defect but there had been athletes with this. Anyone have any ideas about what can of routines I should focus on to build up what Pec muscles I do have
This is such an peculiar medical condition that I’m pretty sure the only advice you’ll get here is to just train as best and as “normal” as you can. Do your best on all sorts of chest presses on various angles, dips (if you can), and flyes.
We’re not exactly talking about how to bench if you’re shoulder-dominant, this is a pretty major physiological issue and the body is pretty much designed to have muscles takeover the work in unique/significant situations like this. So on one hand, you’re only going to be able to do so much.
Like Chris said, can’t really offer any advice. I did, however, recently read about someone with a very similar situation who is looking to complete in Physique. Search Gunnar Anderson Physique.