Nice attention to anatomy! I love how the muscles look like their in motion (something I have not accomplished just yet)! I don't think I've seen the new book, I'll have to check it out. in the meantime, FAV!!!
If you really want to accomplish motion in those muscles, try this book! It is the best book I've read on making the movement come alive. I drew this study directly from a marvel book, but what taught me balance for the anatomy was learning about force.
Force: Dynamic Life Drawing for Animators / Edition 2 by Mike Mattesi, Michael D. Mattesi