Front and Back Arm Lines
Front Arm Line
Front and Back Arm Lines: When we look at the way the muscles of the arms work together, we see that the arms are divided into a front and back arm line, with the thumb, radius, inner forearm, biceps and pectorals muscles in the front line and the pinky edge, ulna, back of forearm, triceps, rotator cuff, deltoids, rhomboids and levator scapulae composing the back arm line. If you hold your arms up and out to a “T” position, with palms facing forward, you would be displaying your superficial and deep front arm lines in the front of the body, and the superficial and deep back arm lines behind you.
The Deep Front Arm Line begins with the pec minor, originating at the 3/4/5 ribs, and connecting to coracoid process of the scapula. The pec minor elevates the upper ribs to support respiration when you are desperate, but too often it is over utilized to aid in shallow, rapid mouth breathing that we all get stuck in at our computers and beyond. This over compensation of the pec minor as a muscle of respiration often makes it short and tight, and due to its insertion point at the coracoid process, can actually pull the scapulas forward into a slouching position over time. As Thomas Meyer’s jokes in his book, “In normal ‘arms down’ posture, shortness in the proximal DFAL simply pulls the coracoid process down to create anterior tilt in the scapula, creating the rounded shoulders commonly commented upon by your mother.” Viewing from the side, this would mean that your shoulder blades look more like the slope of a roof, instead of hanging vertically like a cliff. Pec minor tightness also results in the shoulders and ribs moving together when you breathe, due to excessive upper chest breathing.
Pec Minor: Excessive tightness in the pec minor can negatively affect breathing, head and shoulder posture and overall function of the arms, so it can be helpful to isolate the pec minor with a few stretches in order to open the chest during classes, or after working with the shoulders. Take time to neutralize the ribs before and during the exercise though, as they will tend to flare up to avoid the stretch itself.
PEC MINOR stretches
Stabilizing through Deep arm Line: The clavipectoral connective tissue that surround the pec minor gives it a large anchor along the top 6 ribs. This fascia also links the work of the pec minor to the biceps brachii, especially when the arms are horizontal and above, like in a bear hug, plank position or downward dog. The line continues out across the inner forearm and and the flexors of the hand. You can feel the connection between the bicep and the radius and thumb edge of the hand by rotating the arm at the elbow, like turning a door knob, and watching the bicep shorten and lengthen.
Overall the deep Front arm line is a stabilizing line, helping to manage and mitigate side to side movement like we see in plank position. If we always try to maintain a rigid plank position, for example, we might be missing the opportunity to awaken this mitigating potential of our deep front arm line. For that reason it can be beneficial to add a little sway or rock to your table, planks and dog postures.
Swaying front arm line exercise
Superficial Front Arm Line: The more superficial aspects of the front line include the pec major and latisumus dorsi, which create an entire circle of support and mobility surrounding the shoulder. “Between the pectoralis major and the latissimus, the SFAL has nearly an entire circle of attachments, reflecting the wide degree of control the SFAL exerts on movement of the arm in front of and to the side of the body (Fig. 7.13).” These muscles provide the force for large movements of adduction and extension, like you would encounter in reverse table or plank, or when transition from side plank back to plank position.
Back Arm Line
From Spine to Fingertips: “The SBAL is a single fascial unity from the spine to the backs of the fingertips”. A single fascial unity that covers such a huge expanse of space, our back arm line is built for support and stability. The muscles are hardly separate and can almost be seen as one large swath across the back and over the shoulders.
Muscles of SBAL: The back arm line anchors us with support, working out from the trapezius and rhomboids, with strong axial skeleton connections, and then out through the rotator cuff, providing the shoulder socket itself with support, and down the back of the arm through the triceps— which are typically bigger than the biceps in most body types, having three heads and more mass, down to the Olcranon and pinky edge of the hand, the stabilizing force of the forearm.
The Source of Hand Eye Coordination: From the upper thoracic spine, the rhomboid begins the deep back arm line and immediately sandwich the scapulas via the rotator cuff muscles. The rotator muscles surround the head of humerus just like the ocular muscles surround the eye
“These four muscles of the rotator cuff control the rounded head of the humerus in much the same way as the ocular muscles control the orbit of the eye…’The brain points the arm and finger as accurately as it points the eye. In the orbit and at the shoulder, the eye and the humerus are free to rotate (or swing) in front-to-back and side-to-side planes, and also around their long axes. And in both cases there is a precise arrangement of muscles aligned and attached to power each of these movements.” - Frank Wilson, from his book, The Hand
When asked how he shoots so well, Wild Bill Hickock, one of the greatest marksmen of all time, said he just looks at what he wants to shoot. SO simple, yet biologically so true.
Traps & Delts: This deeper back arm line continues through the triceps, with origins on the back of the shoulder joint and humerus, and then wrapping around to the olecranon of the ulna, your elbow. This line continues to the outside of the pinky finger. The more superficial back arm line consists primarily of the Trapezius and Deltoid
It is worth noting how the deltoids and trapezius muscle fibers align, pointing towards their capacity to work as a team. The anterior fibers of the deltoid align with the upper trapezius fibers. This muscular flow continues to the middle fibers of the deltoid and middle trapezius fibers. And of course finishes with the posterior fibers of the shoulder aligning with the lower trapezius fibers.
This is why Thomas Meyers argues that “The trapezio-deltoid complex can be seen as one large triangular muscle that focuses down on the outside of the humerus from a broad attachment along the whole upper spine.”
Skillful Set Up: The goal of understanding the nuances of the front and back arm line, and their connection points, is to help us feel support from more angles while we interact with our arms and shoulders in postures. It is all too common to depend on the superficial aspects of a muscle group, such as the biceps and pec major as we squeeze our elbows together in headstand— but although this might give you a sense of stability, it neglects the dance of stability at work in the shoulders. There are ways that we can skillfully set up our postures to better allow for this dance to take place.
For example, in headstand, its common to clasp the hands together behind the head in order to harness the strong and superficial Deltoids and Biceps. Although this may feel like its giving you more control in the posture, it comes at the expense of using the posture to better balance the front and back, as well as deep and superficial arm lines. We might carry this mountain today, but we are missing a golden opportunity use this moment to grow.
An easy solution is release the grip of the hands, and instead place them on the mat in a triangular shape, as seen in the slide. This prevents the fall into doership, and specifically forces us to work across the many layers and dimensions of our arm lines.
The same is true in side plank, as we rotate from our setup in regular plank to the side posture and back again, promoting greater and greater interaction between the shoulder muscles
We see that the arm lines are meant to dance together, supporting not only each other, but also dancing with the core and axial skeleton in support. As we read earlier, “The deep front arm line is primarily a stabilizing line,” and this same support follows us to the back line, as we see that “The Back arm line…acts mostly to limit and contain the work of the front arm line.” In other words, they dance together towards support.