As we know well from core work (and trying to get that six pack), completely isolating a muscle group is a strategy that will likely backfire. You need to pay attention to your foundation — starting the big, functional movements, and then zero in on your weaker parts. After that, add volume to the areas that need the most improvement, exploit your weaknesses, and muscle will grow. Here’s how to put it all together for bigger, well-defined arms.
Source Link - https://www.mensjournal.com/health-fitness/how-to-get-bigger-arms-20150422/