Hello! In our previous lesson, we mapped out the muscles on the front of the torso: the pectoralis major, rectus abdominis, and external obliques. We focused on how they connect the ribcage and pelvis, and how they squash and stretch with movement.
Today, we'll turn our attention to the posterior side and complete our study of the torso's musculature. The back is a complex landscape of overlapping muscles, but we're going to simplify it by focusing on the three major groups that define its form. Our goal is to identify and draw the trapezius, the latissimus dorsi, and the erector spinae. Understanding these three groups is the key to constructing a believable and dynamic human back.
1. An Overview of the Back Muscles
The surface form of the back is dominated by three powerful muscle groups. Let's start by getting a quick visual layout of our subjects for today.
We will break down each of these muscles, looking at their specific shapes, locations, and how you can simplify them for drawing.
2. The Trapezius ("Traps")
The trapezius is a large, superficial muscle that covers the back of the neck and the upper back. Its primary functions involve moving the scapula (shoulder blade). For artists, it's often simplified into a memorable shape.
Figure Drawing: Design and Invention
The book Figure Drawing: Design and Invention by Michael Hampton provides an excellent simplification for the trapezius. This will help you see it not as a complex muscle, but as a simple, manageable shape.
Read the sections 'TRAPEZIUS — GESTURE' and 'TRAPEZIUS — SHAPE' (found on pages 99-100 of the PDF). Focus on the concept of simplifying the trapezius into an 'upside-down dagger' shape.
This "dagger" shape is a powerful tool for construction. The handle sits at the base of the skull, the crossguard extends out to the shoulders, and the blade tapers down the spine.
Let's see this muscle on a 3D model to understand how it relates to the skeleton.
Understanding the Back Muscles Anatomy of the Torso for Artists
The video 'Understanding the Back Muscles' by Victory3D provides a clear visualization of the trapezius and its connections.
Watch from 07:50 to 09:15. Pay attention to how the instructor traces the 'diamond shape' of the trapezius. Notice its key attachment points: the base of the skull, the spine of the scapula, and the vertebrae of the upper back.
3. The Latissimus Dorsi ("Lats")
The latissimus dorsi is the largest muscle of the back. It's the muscle that gives the torso its characteristic "V-taper," especially in athletic individuals. It's a powerful pulling muscle, used in activities like rock climbing or swimming.
Drawing Lower Back Muscles - Anatomy & Motion
The Proko channel offers a fantastic breakdown of the lats in the video 'Drawing Lower Back Muscles - Anatomy & Motion'. This segment will explain the muscle's extensive origin and how it cleverly inserts into the arm bone.
Watch from 02:16 to 05:19. Focus on these key points: Origin: It starts all the way down at the pelvis and lower spine. Insertion: It twists around to insert on the front of the humerus (upper arm bone). V-Shape: Understand how this broad origin and narrow insertion creates the famous V-shape. Overlap: Note how it overlaps the teres major muscle and is itself overlapped by the lower part of the trapezius.
Like the trapezius, the lats can also be simplified. Michael Hampton describes it as a "bowl with arms and legs," which helps visualize how it wraps around the cylindrical form of the ribcage.
4. The Erector Spinae
The erector spinae are a group of deep muscles that run vertically along both sides of the spinal column. Their main job is to keep the spine erect (straight). While they are mostly covered by the trapezius and lats, they create a very distinct form in the lower back.
Let's turn back to Proko for a clear explanation of this muscle group.
Drawing Lower Back Muscles - Anatomy & Motion
This first part of the Proko video focuses exclusively on the erector spinae.
Watch from 00:37 to 02:15. Pay close attention to: Form: They look like two thick, cylindrical rods on either side of a central valley (the spine). Surface Appearance: Notice how they are visible in the lower back, pushing up from underneath the thin aponeurosis (tendon) of the latissimus dorsi. Antagonist: It's useful to know they are the antagonist to the rectus abdominis we learned about in the last lesson. One flexes the spine, the other extends it.
The simplified shape to remember for the erector spinae, as per Michael Hampton, is "two corn dogs side-by-side," creating the columns that define the lower back.
5. Practice: Constructing the Back
Now it's time to combine this knowledge into a structured drawing process in Procreate. We'll use a step-by-step method that builds the back from the inside out.
How to Draw the Human Back, a Step-by-Step Construction Guide
The Gvaat.com article, 'How to Draw the Human Back, a Step-by-Step Construction Guide,' provides a logical process for drawing the back. We will use its method for our exercise.
Read the section 'Step-by-step construction of the back'. You don't need to read the whole article, just familiarize yourself with the 7-step process outlined in this section. We will be adapting it slightly.
Exercise: Constructing the Back (20 minutes)
- Find a Reference: Find a clear photo of a human back. Search for "male fitness model back" or "anatomy pose back" on Pinterest or a stock photo site. A more muscular figure will make the forms easier to identify initially. Import it into Procreate.
- Step 1: Core Forms & Gesture (New Layer): As we've done before, start by lightly sketching the simple forms of the ribcage (egg shape) and pelvis (block shape). Draw the C or S curve of the spine connecting them. Pay attention to the tilt and twist of these forms.
- Step 2: Landmarks (Same Layer): Locate and mark the spine of the scapulae (shoulder blades). This is the most critical landmark for building the upper back.
- Step 3: Connect the Trapezius (New Layer, Red Color): Using the "upside-down dagger" idea, draw the trapezius. Start from the base of the neck, connect it out to the spines of the scapulae you just drew, and then taper it down the center of the back.
- Step 4: Draw the Lats (New Layer, Blue Color): Draw the large V-shape of the latissimus dorsi. It should start from the lower back/pelvis area and sweep up and around the ribcage, tucking in towards the armpits. Note how it overlaps the bottom tip of the scapulae.
- Step 5: Indicate the Erector Spinae (New Layer, Green Color): In the lower back, between the start of the lats, draw two vertical columns on either side of the spine to represent the erector spinae.
- Step 6: Refine (New Layer, Black/Gray): Hide your colored construction layers. Using them as a guide, create a new line drawing that refines these shapes into a cohesive whole. Focus on how the muscles overlap and interact.
Conclusion
Great job! You have now assembled the major muscles of the entire torso. While the back can seem intimidating, breaking it down into these three primary muscle groups makes it much more approachable.
Key Takeaways:
- The Trapezius is the kite-shaped muscle of the upper back, best simplified as an "upside-down dagger."
- The Latissimus Dorsi is the large, V-shaped muscle that defines the width of the torso.
- The Erector Spinae are the two vertical columns that run along the spine, most visible in the lower back.
- A constructive approach is key: start with the skeleton (spine, ribcage, scapula) before adding the muscle masses.
In our next lesson, we will focus on the deltoid muscle. We'll see how it creates the rounded form of the shoulder and acts as a bridge connecting the torso to the arm, linking directly to the trapezius we studied today.