Wow, this is extremely good. I wondered if anyone was going to do umbohr and this is an excellent impersonation!
Love the pose and the anatomy looks great. Very beautiful shading—I love how well you've conveyed the structures under the skin, especially the ribcage.
Really inspirational 
Thanks! I used reference photo and even with that I think I missed a lot of anathomy nuances with that shading. But as first try of doing something like this I'll let it go x)