I want to share what I know about painting the human back, which is one of the most commonly avoided anatomical subjects and one of the most beautiful when done well.

The back anatomy: the trapezius is the large muscle that dominates the upper back, running from the neck to the shoulder blades and down to the mid-thorax. The latissimus dorsi is the large fan-shaped muscle that fills the lower and mid back. Between the shoulder blades, the scapulae create distinctive surface features depending on arm position.

Arm position effects: when the arm raises forward, the scapula rotates — the bottom tip moves outward and the shoulder blade becomes more visible on the back surface. When the arm is at rest, the scapula lies relatively flat. These scapula position changes are what make the back feel dynamic or static.

The spine: a visible groove or line at midline is produced by the spinous processes and the surrounding muscle valleys. It's not uniform — at the thoracic level it's more pronounced; at the lumbar level it may be hidden by developed muscle.