Hey welcome back to Proko! Last time we learned the basic anatomical stuff and motion of the
shoulder muscles. And we identified and understood the muscles on a model. Great, but now let's
focus on why we're here - how to draw the shoulder muscles.
Infraspinatus
The infraspinatus is flat and simple. It has a convex form, like all muscles do, but the
convexity is usually subtle. Like a... fluffy pancake. It'll appear as a recessed plane
since the surrounding muscles bulge out. However, when the infraspinatus is active and really
developed, it can also bulge out. You might see the infraspinatus split into two bumps.
In this photo it's split down the middle. But, this split can be confusing. In this
photo, this is the large shape of the infraspinatus. The split takes a curved, more vertical path.
Not what you'd expect.
Let's move on to the teres minor. Like I said before, the teres minor isn't always visible.
On the surface in can appear as a continuation of the infraspinatus, or a depression, since
the infraspinatus and teres major travel above it. But when you do see it on an ultra ripped
superbeing, remember “teres” means cylindrical and that's exactly its form.
Teres Major
The teres major is also a cylindrical muscle, but it's much larger. The teres major is visible
on most people, even thin women. That's why it's such a great landmark. It's that bump
on the outer contour of the back, near the armpit. When the arms are at rest, the infraspinatus
and teres minor stay flat but the teres major is squashed and stands out. When the arms
are raised, the teres major is stretched, so the cylinder gets thinner. Its form become
less visible, but the double-curve of the back becomes clearer. What is that, you ask?
Well... The latissimus dorsi dominantes the contour of the back with its strong upwards
angle. But the teres major cuts across the latissimus to get to its insertion. This creates
a double curve. The latissimus has the longer, more vertical angle, and the teres major is
that short, more horizontal angle near the armpit. If you only remember one muscle today,
make it the teres major! It's visible on nearly everybody and it's helpful for locating other
muscles. Thank you, teres major.
Serratus Anterior
The serratus anterior makes a fan-like shape as it reaches out from behind the scapula
to wrap around the rib cage. The attachments to the ribs follow an arc somewhat parallel
to the skeletal arch. It's largely covered up by the pectoralis major in the top front
and the latissimus dorsi in the back. Usually, only the tips of the lowest 4 digits are subcutaneous,
progressively getting smaller as they attach closer to the lats. Individually, each digit
has a cylindrical form, and that's clearest where they interlock with the external oblique
digits. The serratus digits are more horizontal and rounder than their oblique neighbors,
so there will be instances when you'll see the serratus, as the oblique digits stay flat.
On the back, the latissimus dorsi completely overlaps the serratus, but sometimes the volume
of the serratus is thick enough to push out and be visible anyway. If so, the serratus
will appear as a large round form arcing from the bottom of the scapula to the flank of
the oblique. So, when the lat is flexed, we'll see the cylindrical form of the lat. When
the lat is relaxed, we'll see the serratus.
Assignment
Invent the back muscles! Draw the rib cage, scapula and humerus as simple planar forms.
Then add the shoulder muscles. Try out different poses and angles. If inventing is a bit too
challenging for you, start by using photo reference or the Skelly app, and ease in to
invention. You can get the Skelly app at proko.com/skellyapp. I also have model photos available at proko.com/poses,
you can get a free model sampler pack in the description below.
Inventing the Shoulder Muscles
To watch me demonstrate how to invent the shoulder muscles
go to proko.com/anatomy
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