Shoulder looks pretty good, I don't see anything there that would concern me.

Couple really minor things, not issues/problems really, just a couple personal preference nitpicks.

I would probably shift the poles on the back in a row or two, keep the same flow, still the same number of columns and what not, just shift them to the left a column or two. That gets them a little further away from the bulk of the deformation/stretching, but they're also a  good shape/flow to help define the muscle/bone of the shoulder blade area a bit if you wanted.

I'd also maybe move that pole in the elbow down a couple rows away from the joint. I know where it is know, it does a good job of creating that indent where the head of the bicep comes into the elbow, but there's some potential for it to get wonky when bending the elbow, and you can use that extra geometry a little further down the forearm to get some definition where the muscle comes over the radius bone.

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