Sorry but honestly these are like the coolest detail in male anatomy, the under-arm rib muscle thingies! Like just imagine a toxic green underbelly fading into a stripe of brilliant red before a solid dark grey-black!
Day Draw the anatomy of the shoulder and arm to the wrist. Anterior and posterior views. Filled with arm angle references - via ? --> 팔 그리는 방법 팔의 움직임 . lol, it's visually helpful if you can't read it like I can't