I in fact believe that musculature is an important part of this trope. Even when not displaying the character in a typical post, comic book artists will go to great lengths to layer upon layer muscles and their definition onto the heroes bodies. Male and female forms will have have their body structure in fact strongly impressed upon us by the muscular definition and in some bad cases that leads to what, when you think about it, must be a body missing some joints and bones in important cases. Muscles that you probably just wouldn't so developed on a normal person such as the Serratus Anterior (aka Boxer's Muscles or "The things that seem to be bursting out of Superman's ribs all the time") or the lower insertion of the obliques being highly peaked to emphasise female hips (see every bad dr