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Monday, August 17, 2015

The Posterior Sling [Guest Post by Dawn Lewis]

Written by Dawn Lewis

The posterior sling is comprised of the latissimus dorsi muscle on one side of the body, the
ipsilateral or same side thoracolumbar fascia and then transferring to the opposite side or
contralateral thoracolumbar fascia and the opposite side gluteus maximus.  We will explore the
implications of this in 3 ways:

1) Latissimus dorsi inserts on the medial lip of the intertubercular groove of the humerus and all of the muscles direct actions happen at the shoulder.  These actions are medial rotation of the arm at the shoulder, adduction of the arm at the shoulder, and extension of the arm at the shoulder.  Many clients have one or both shoulders that are stuck, for lack of a better word, in medial rotation.  This pattern chronically shortens latissimus dorsi, fibers of which blend with the thoracolumbar fascia.
This has the potential to shorten the thoracolumbar fascia on the same side and the opposite side of the body.  Gluteus maximus originates from the thoracolumbar fascia directly and from the gluteal aponeurosis (as well as from the iliac crest, sacrum, and coccyx), which is a continuation of the thoracolumbar fascia.  If the thoracolumbar fascia is shortened it has the potential to shorten the fibers of gluteus maximus.

So, we see that tension patterns at the shoulder can affect the entire posterior sling.  If we travel
further down the body we find that gluteus maximus inserts on the iliotibial band.  The IT band then
inserts on the lateral condyle of the tibia at Gerdy's tubercle.  This means that if a client has a tight
IT band on the right side, and/or knee issues on the right side, the issue could very easily be the left
shoulder.  And this leaves out the why of the shoulder pattern.  Is the shoulder in medial rotation
because of activity, the forearm being overpronated, and/or forward head syndrome?  The entire
pattern and the knee pain could be caused by what is moving the shoulder into the pattern of

2)  Beginning at the foot, we can follow the pattern from the position of the foot to the shoulder in a few muscles or fascial structures.  Let's say that the client's right foot is oversupinated (turned in with an accentuated arch).  This position generally causes tension in tibialis anterior and peroneus longus.  Tibialis anterior because one of its two actions is supination (or inversion) and peroneus longus because the majority of the force coming through the foot will be coming through the lateral side of the foot, shortening the joints and the muscles along the lateral line of the lower leg.  Tibialis anterior originates from the lateral tibia and peroneus longus from the upper fibula.  As these muscles tighten they can pull the tibia into lateral rotation at the knee.

This knee position will tighten the IT band, whose job it is to stabilize the knee.  When the IT band
tightens, the muscles attaching to the IT band, namely gluteus maximus and tensor fasciae latae,
tighten as well.  The shortening of gluteus maximus can then lead to tautness in the thoracolumbar
fascia.  Now we are into the posterior sling, and it is easy to see how tautness in the thoracolumbar
fascia could lead to tension in latissimus dorsi.  If we follow the posterior sling, the latissimus dorsi
tension would be on the contralateral side, in this case the left side.  This tension has the potential
to pull the left shoulder into medial rotation, as well as adduction and extension. All of this shows
that the pattern in the left shoulder could very easily be coming from the right foot.

3)  Finally, we would be remiss to leave out the bones that the muscles attach to, so let's take into
account the bony anatomy and how it could affect the posterior sling or how the posterior sling
could effect it.  When we talk about the first synopsis above, we need to ask why latissimus dorsi
has shortened and pulled the shoulder into medial rotation.  Most often the muscle tightens first
and the joint moves into the muscle's actions.  But sometimes the muscle is tight because of what is
happening with the bones.  In this example, it is possible that latissimus dorsi became tight because
the humerus moved into medial rotation.  Why would the humerus move into medial rotation?
Possibly to accommodate the radius and the ulna.

As I sit and type this article, I pull my shoulders back and I move the humeral heads out into external
rotation.  But my hands on the keyboard keep my forearms in pronation.  If this is my position a
good portion of each of my days, my body will decide that through my actions I am telling it that my
forearms belong in pronation.  My supination will become more and more limited.  If my radius and
ulna are in an overpronated position, but my humeri are sitting neutral between medial and lateral
rotation, I will have pain in my elbows.  To stop this pain, each radius and ulna will recruit their
respective humerus and each humerus will slowly be pulled into the pattern that began in my
forearms.  As the humeri moves into medial rotation, fibers of latissimus dorsi shorten.  Thus begins
the posterior sling pattern.

If we look at the second synopsis above we begin with the position of the ankle.  The foot is in
oversupination, which moves the talus lateral.  One joint in the ankle complex, the talocrural joint, is
an articulation between the talus and the tibia.  When the talus moves lateral it will likely recruit the
tibia and the tibia will move lateral.  Now, we know that tibialis anterior and peroneus longus are
shortened, and when the tibia moves lateral we will also get shortening of and tension in the lateral
head of gastrocnemius, the lateral fibers of soleus, and extensor digitorum longus.  When the
movement of the bone is coupled with this muscle tension on the lateral side of the lower leg the
tibia is prone to lateral rotation.

So, what began at the ankle has now shifted the tibia out of its natural pocket.  As soon as this
happens we have excess tension in the IT band, which is an insertion site for gluteus maximus,
which is the distal end of the posterior sling, which we could follow all the way back up to the contralateral shoulder.

Whew!!  And this does not include any discussion about angonist/antagonist relationships and how
these patterns lead to facilitated and inhibited muscles.

As we know, the entire body is connected in a few short steps.  The posterior sling in one way to
think about systemic compensation patterns and what effects what.

Dawn Lewis owns Full Circle School and teaches Spontaneous Muscle Release Technique or SMRT. Please check out the Full Circle website for live seminar dates, course videos, free sample videos, and other articles.

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