As the human body moves, muscles contract and relax, creating subtle changes in body contours and shifting patterns of light and shadow on the skin's surface. Visualizing exactly what happens beneath the skin to cause these changes on the surface is of interest to artists, physical therapists and body builders - to anyone who needs to understand the body in motion. This book aims to be a visual aid to drawing, sculpting and learning surface anatomy. A live model is made to look as though his skin has been stripped off - skin muscles, tendons and fascial sheaths having been painted on him - and photographed in multiple poses. For each pose there are paired photographs - one painted and labelled, one not - aiming to help one to grasp how the simulated muscles produce the subtle lights and darks, hills and valleys, on the model's unpainted skin.