Hey! I think your question isn’t really tied to your drawing, but more to arm anatomy in general. That’s a bit tricky to fully explain here, so I’d recommend watching videos that break down how muscles move. For that, you can check out Proko’s channel—he has really great content explaining these concepts for different parts of the body. I’m sure it’ll help a lot! You can also look at breakdowns on ArtStation, where 3D artists share anatomical studies. You’ll often find arms shown from different angles, and sometimes even how the muscles behave in motion. Both of these will help you a lot. One key thing I can mention here is to learn when a muscle is at rest versus when it’s active—this helps you understand when it contracts or stretches (like with the biceps and triceps). Also, it’s very helpful to study how muscles connect to each other, as taught in Artwod. That way, you can draw muscles without relying on exact references every time. Understanding how muscles connect and their underlying forms will take you a long way! Hope this helps :)
