Tonight's Studies (Torso Anatomy)

So.. here's the promised torso anatomy (they are from reference, Drawing School Anatomy book), trying to remember the shape, contours, and placement of the muscles on the torso as I'm drawing, and how it connects with the head and the arms. Also I'm trying really hard to keep things in proportion by gesturing carefully with the side of the pencil first, and then measuring by eye, checking with big shapes first and then going more detailed with the point of the pencil. And then to improve the quality I'm trying to use just a single, confident line to represent the shape and mass of what I'm drawing, thinking all the time about the mass, this is very important as it builds confidence and observation skills.