I shall add this to my favorites, I have an idea, and I enjoyed these "study" pieces, they are well drawn, I've done practice drawings myself, but never really gain much skill at it. Really a cool image.
Wow, you really are working hard! One thing that manga as an overall style tends to depict poorly is the connection of the neck to the head in posing. Not in all cases, but I notice it in many manga, even the talented Mark Crilley draws some weird necks, so I'm glad you are looking at the real anatomy here! No weird necks for you! Great grasp of the musculature.