Anatomy Study- the infraspinatus, teres major, multifidus, and half of the hamstring muscles are missing or miniscule. Mostly attention to where the spine of the scapula is would help round off where the rest of those forms should go, but the ones ON the scapula are tiny and pushed up to make room for those huge lats. Also when you gesture the figure it;s best to make draw measurements for the ribcage and the trapezius seperately, even if they make a nice circle the ribcage is too important structurally to be fused to a muscle in the underlying sketch.
This, after taking an anatomy class with the professor reading off this book for each lecture, I'm sure is one of the best books for anatomy out there. It gives photo examples of every prominent surface muscle on the human body. It's really fun to read.
Flash- you know the problems mostly, but the pecs got squashed from your theory of where the pecs should go in that pose I guess, but they're like 1/3 the size of average pecs, and that looks weird on a superhero. pecs need to be prominent on about every human being.
You're going in the right direction. I like this stuff!
Also the batman looks like a pouting child. Don't compress your poses into sitting like an emo kid. I mean yeah hes batman but batman isnt a queer