For a sculptor, this creates a distinct visual rhythm. The muscular mass of the forearm shifts. In pronation, the muscles on the thumb side of the forearm twist inward. This is best visualized as a "Figure 8" or a towel being wrung out. If you sculpt a forearm without accounting for this twist, the arm will look stiff and broken, regardless of how detailed the muscles are.
Most traditional anatomy books are text-heavy and focus on static models. Arm and Hand in Motion flips this by being 90% visual , treating artists like the visual thinkers they are. Dynamic Deformation arm and hand in motion by anatomy for sculptors pdf better
If you want to take your work further, studying 3D scans and simplified muscle block-outs remains the gold standard for modern artists. For a sculptor, this creates a distinct visual rhythm
The arm begins at the shoulder. In motion, the deltoid acts as the cap of a cylinder. When the arm raises, the deltoid shortens and bulges, but the critical detail for a sculptor is what happens underneath. As the arm abducts (moves away from the body), the armpit (axilla) opens up. The pectoralis major and latissimus dorsi stretch thin, revealing the underlying rib cage. A common mistake is sculpting the shoulder as a ball joint sticking out; in reality, it is a complex folding of skin and muscle over the thorax. This is best visualized as a "Figure 8"