Hey! Nice work! Personally, the forearm muscles are something I still haven’t completely mastered either, and I often forget exactly how they connect to the upper arm. Morphos is a great book to learn anatomy tho :D Anyway! I only noticed one small issue with the arm in the middle. The rotation of the hand is almost impossible as drawn, unless someone has an extraordinary amount of flexibility and can rotate their wrist nearly 180 degrees. Because of that, I rotated the hand a bit less so that the palm faces slightly more toward the deltoid. On top of that, the bicep feels too short and could be extended a little to improve the proportions. As I mentioned earlier, I don’t have the forearm muscles fully memorized myself, so I’m not entirely certain whether that particular muscle would appear exactly that way. One thing you can do to practice is trace the muscles over photos of models or anatomy references. You can either identify each muscle individually or focus on its simplified forms and groupings. This will help you develop a much better understanding of how the muscles connect and relate to one another. Hope this helps!
