The lats & scapula debate

I thought I’d write a quick post to clear up some of the confusion that exists regarding the potential direct interaction between latissimus dorsi and the scapula. I recently read an article on t-nation and while the author never claimed that the lats attached to or directly moved the scapula, some confusion was definitely generated in the comment section. The internet police were out in force that day, quickly citing that the lats don’t attach to the scapula in any way, so there’s no way they could contribute to any of the movements described in the article. Certainly many anatomy books make no mention of any direct interaction, and at best only describe that the lats often overlay the lower portions of the scapula with no direct attachment, but there’s more to the story than that. Ultimately everyone online agreed with their own facts, so an internet flame war was avoided, and the usual rounds of ‘great article’ resumed in the comment thread. Crisis adverted.

But there’s just one problem: in most people, latissimus dorsi actually DOES attach to the scapula!

Latissimus dorsi attaches to the inferior angle of the scapula

Basic anatomy texts can often leave this fact out, as it isn’t present in everyone in the population and there is some debate as to the functional significance should a direct attachment exist. Pouliart et al (1) investigated the anatomy of latissimus dorsi in 100 cadavers and found that in many specimens there was a connection to the scapula as the muscle ran its course to ultimately attach on the humerus. They describe three types of interactions between latissimus dorsi and the inferior angle of the scapula:

  • Type 1, Direct Attachment: muscular slips are anchored directly onto the inferior angle of the scapula.
  • Type 2a, Indirect Attachment: few muscle fibres with a soft, fibrous link between the two (fascia).
  • Type 2b, No Attachment: a bursa and no connective tissue between the two.

The majority of people (79%) had either a Type 1 (direct, 43%) or Type 2a (indirect, 36%) attachment, while the remaining 21% had no attachment at all (Type 2b). So it seems that in the majority of the population, there is some form of link between the latissimus dorsi and the scapula, even if some of us have no direct interaction. These direct muscular slips have been observed by others (2), although not always consistently (3), and I’ve seen them on specimens in the anatomy lab myself as well.

What’s the significance of this?

At this point, it’s hard to tell specifically, however we can make some inferences. Because of the relatively horizontal line of pull of the muscle fibres that run between the inferior angle of the scapula and the thoracic vertebrae, we could suspect that the lats assist in retraction of the scapula (pulling the shoulder blades back and together). The lats wouldn’t be the primary contributor to this movement, and for pure retraction to take place it would have to be coupled to the activity of other muscles such as the rhomboids.

This interaction could also contribute to downward rotation of the scapula – fitting, as this would allow for a direct link between scapula and humerus during shoulder adduction (bringing the arm down towards the side of the body). As latissimus dorsi contracts, fibres anchored to the inferior angle will pull it towards the midline of the body (superiomedial) and create rotation through an axis near the superior (medial) angle and the spine of the scapula.

Or maybe as the original authors suspected, the lats simply stabilize the shoulder via it’s insertion on the humerus and perform the functions at the shoulder we’re familiar with including adduction, extension and medial (internal) rotation (1). There definitely isn’t too much discussion of the scapular attachments from a functional perspective in any of the articles I’ve cited below.

Anatomy isn’t set in stone

We often think of anatomy as a ‘hard science’ but arguably the most important lesson here is that there can actually be significant variability between people. When you get into the specific functions of each muscle, you’ll see there’s actually more debate than you realized. Sure you won’t find too much argument about the biceps or the triceps, but when you start to look more specifically at muscles and movements, especially complex areas like the scapula, you’ll find that it’s definitely a more complicated subject than we often make it out to be.

Comments

    Dan DeFigio says:

    Thanks for a great report! Well written.

    rodrigo says:

    very interesting, in fact I was sure about latissimus always attached to the scapula, so I’ve learned something new. It’s amazing to see anatomy like a living-evolving thing and not as set in stone. Thanks for your article.

    Justin says:

    Just wanted to say thank you for clearing this up for me and respect for the strong referencing.
    Cheers,
    Justin

    […] back muscle, has the function of adduction, extension and internal rotation of the shoulder, but in most people it also connects to the scapula and serves to retract it. Therefore, reaching full retraction means […]

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Dan Ogborn