You seem to have a really good understanding of anatomy, and lighting too
To speed things up a bit, try to simplify some of the shapes a bit more. Focus on the overall picture and direction of the pose before you start drawing individual limbs. The top of the torso can be one oval, the hips another, the arms/legs as cylinders, etc. You can make them accurate to the exact form later.
Creating the line of action- the line that follows the curve of the spine- can also help with time. All of the limbs should follow along the curve of this line, so you don't have to worry about their individual placement.
Overall, nice work!! :)
