You have a good understanding on the anatomy already! What I can see is that the poses themselves seem to be somewhat stiff. I suggest you try looking up how to do gesture drawings! Once you improve your understanding of anatomy, you can try to watch gesture drawings videos :)! Though keep in mind, gesture drawings are supposed to be quick, and more for the feeling rather than pure accuracy, but it can help!
or you can look up for artbooks about anatomy! - Art student
or you can look up for artbooks about anatomy! - Art student