I made this model some months ago but I never shared it before so here it is!
For this study I started as usual from the depth to have a better understanding of its anatomy. I created a skeletal system base and thanks to this I was able to reproduce an accurate muscular system for that pose.
Would you like to see them? I never made a proper render for those pieces but I think it would be nice to set-up them as well and share the complete process I followed.