Spherical shapes are the next step in the human drawing process. Knowing how to draw spherical shapes is important for this process, as well as knowing how to draw cylinders. Again, when drawing these type of sketches, only focus on the overall mass and keep proportions constant. Dividing the torso into hips/ ribcage really helps, especially later on. Think about how the shapes go back in space, and if you have trouble on how things go back in space, study perspective to get a better understanding. A mannequin was used to help draw this. I recommend buying one at a local art store.