Wow, thanks so much for sharing these! I'm just now joining Line of Action, and I'm really happy to have found your work :)
Hiya!
There's no doubt that you have a great understanding of form and drawing. I do not have the experience or practice that you've put in to the art.
The one thing you could improve would probably be the understanding of anatomy, specifically with muscle structure. I understand that these were done in very short time, but there are a few drawings that show less perfection.
The feeling I'm getting is that - when you see the thigh, you draw the shape it creates, without fully giving the different muscle groups credit. The product is something that's shaped like a thigh, but a little less convincing than the real one.
I can see this happen with the back as well, and certainly the faces.
I think you've mastered drawing what's on the surface. Learning what's inside (anatomy) and learning the shorthands for them, I believe, will send you to the next level.
Thanks so much for sharing your work with us.