Like most areas of the body, the posterior torso has several layers of muscle. When rendering most areas of the body, we artists tend to think primarily about the superficial muscle layers-- the ones that are visible at the surface and contribute most to the body's outward appearance. But things are a little different on the posterior torso. Its muscles are exceptionally broad, thin, and flat, which means we sometimes can see deeper muscles showing right through them. This is pretty cool, but it does make things a little more confusing.
In fact, sometimes the deeper muscles of the posterior torso show more clearly on the surface than the superficial muscles. How can that be? This happens because the superficial muscles are often so thin and flat that they just don't look like much on the surface. But the muscles underneath them are rounder and more defined, so it's actually easier to pick out their shapes.
There are some wonderful examples of this in the figure renderings of Brian Skol. Brian is a student at the Ravenswood Atelier in Chicago, and during his time there he has developed a solid, stunning figure drawing technique and turned out an impressive collection of work. Brian also took my Anatomy course at AAA several years back, and while he is among several top students who mastered the class, he is distinctive in that he's the only one who's ever said the Anatomy final exam was not difficult enough! This comment was unexpected and refreshing, as I'm used to hearing just the opposite.
Several of Brian's figure drawings lovingly demonstrate the posterior torso landscape, but today (and in a few upcoming posts) we'll concentrate on this one. First let's look at the subtle ridges that help define the structure of the back.
I know, I know. I did say subtle, right? But part of the beauty of the human body is that so much of it is a mystery; its structures are always there, doing their job, making things happen, but many don't necessarily need to be right in your face; they'd prefer to stay under the radar and let you discover them.
So let's take a closer look at these shy little devils. The first step in this process was to block in some overall muscle shapes and a few bony landmarks, then to identify them.
Now let's take a look at the ridges that are so beautifully and accurately rendered in Brian's drawing. We'll start with ridge number 1, where the lumbar sheath meets the latissimus dorsi muscle. First, here's how these structures look from a direct posterior view.
You might recall this image from my first posterior torso post. At that time we looked at the relationships of the larger back muscles and the small triangular window they form (in which we can see some smaller muscles on the posterior surface of the scapula.) Now let's use this image to look at the landscape of the lower back. Occupying most of its space is the lumbar sheath, a diamond shaped aponeurosis (which is broad, flat, tendinous muscle covering.) The lumbar sheath serves as an origin point for the large bilateral latissimus dorsi muscles that run across the lower back and sides. Because the lumbar sheath is not muscle tissue, doesn't bulk up with use. So it can appear somewhat flat in comparison to the lumbar sheath. This means we can often see a ridge where these two structures meet. That's what we're seeing on the area labeled number 1 on Brian's drawing.
In this next image, the basic shapes of latissimus dorsi and the lumbar sheath are placed on top of Brian's rendering. This shows the placement of the individual structures and their meeting point.
We can see here that both the latissimus dorsi muscle and the external oblique form borders around the lumbar sheath. The angles of these borders give the lumbar sheath its diamond shape. On a more muscular individual, the flat lumbar sheath would stand out more obviously against the surrounding muscles and would become even more visible.
I am looking forwarding to explaining the other four ridges that can be seen in this lovely rendering, but this is getting a little long, so I'm going to sign off for now. I will cover ridges 2 through 5 in an upcoming post, and I'm also working on the rest of the elbow joint posts. See you soon!