The year is 1988, Crocodile Dundee 2 just hit the big screen and pork chops are only 40 cents per pound. It is also a great year because Serge Gracovetsky wrote his theory of human motion called “The Spinal Engine.”

Gracovetsky developed this theory when he realized that quadruple amputees could essentially walk on the bones at the bases of their pelvises through rotation. From this realization, he began believing that spinal rotation is at the base of human movement.

His theory has evolved over time to include these interconnected parts of our body called “slings.” These slings are made up of muscles and connective tissues and help us produce, transmit, and control the forces that occur in our body. Why should you care about these slings? Because training them effectively will make you more efficient, reduce your chance of injury, and decrease the pain that you’re probably in. Also, they are a large part of the core training that you should be doing. And no, I’m not just talking about doing flutter kicks and Russian twists at the end of your workout.

The Slings

Let’s talk about exactly what these slings are. Like I said, they are a series of interconnected muscles, fascia, ligaments, and tendons, that stretch from one part of the body to another. All of these slings go from the upper body to the lower body, crossing the pelvis on the way there. This is important because these slings help stabilize the pelvis and lumbar spine, as well as transmit forces efficiently and effectively (if they work properly) from the upper body to the lower body (or vice-versa) through the pelvis.

For this spinal engine to be efficient and effective, we need to also make sure that each of these slings are doing their job and not having to pick up for anybody else’s slack. For us to be pain free, efficient, and injury risk free, our slings must be producing balanced energy in the appropriate directions. When working in unison, these slings will help create stability and mobility, especially through the lumbo-pelvic region (the area where your lumbar spine and pelvis meet).

Before I discuss the individual slings, it is important to understand how important they are. The passive structures of the spine and pelvis, meaning the discs and the where the sacrum attaches to the pelvis (sacroiliac joint), can withstand 90 newtons of force before buckling. This is if you stripped all of the muscles and connective tissues away and just put the spine under load. To be honest, I don’t know what 90 newtons means in terms of actual force, but it doesn’t sound like much.

Here is where it gets interesting. Research tells us that the body can be subject to forces of up to 1500 newtons traveling through the spine. 1500 is a larger number than 90 by a lot, so this seems significant. That means that the structures around the spine make it 17 times stronger. That is in large part thanks to the slings that wrap around your spine and pelvis.

You have 4 major slings: the Anterior Oblique Sling, Posterior Oblique Sling, Deep Longitudinal Sling, and Lateral Sling. We will be discussing the anterior and posterior oblique slings today.

The Anterior Oblique Sling

The anterior oblique sling, or AOS, is composed of the obliques, which are then connected to the opposite side adductor (inner thigh) muscles via the adductor-abdominal fascia. Picture fascia as connective tissue, almost like a really tight compression shirt that connects one muscle to another.

While walking, the AOS is very important. Right before you plant your heel down, the AOS rotates your pelvis forward to optimize your body position over the stance leg (the leg that is about to plant down). This helps improve the transfer of forces to stabilize the trunk and pelvis while walking. Also, it will help pull the leg forward while walking.

You can see that the fiber direction criss-crosses the body. This means that the AOS is really important in helping us rotate, as I alluded to earlier. Think of any field sport such as soccer or football. Are you only just running forward or backward? No, of course not. You run, you cut, you turn, you spin, you kick, you throw. All of this rotation is aided by the anterior oblique sling (with help from it’s buddy, the posterior oblique sling).

So, if the AOS is so important, how do we train it? Well, rotational exercises would be a great place to start. All rotational exercises will train both the anterior and posterior oblique slings simultaneously; however, we can target one or the other through our positioning. As an example, here I am doing a Cable Rotation to Press in an AOS Split Kneeling Stance. This AOS targeted stance ensures that the main concentric (shortening) muscle action occurs at the anterior oblique sling.

The Posterior Oblique Sling

Like I hinted at, the anterior oblique sling works in harmony with the posterior oblique sling (POS) to generate rotational forces throughout the body. It also helps aid in supporting functional movements such as gait. The POS is made up of the latissimus dorsi, thoracolumbar fascia, and gluteus maximus.

You see, we are upright creatures. However, back in our more chimp-like state, that wasn’t the case. If we look at our ancestry in our chimpanzee relatives, we can see that their gluteus maximus (butt cheek) muscles are not very large. This is not the case for us. As we evolved to be more upright, the posterior (back side) aspect of our body became more important. So much so that that gluteus maximus muscle became the largest muscle in the body. It works hand in hand with the latissimus dorsi in the upper body to create the sling across the back of your body.

This sling is very important in walking as it creates extension through your hip and upper body during the stance phase when your foot is flat on the ground. This extension force propels us forward. Now, you might not think that the lats need to do much here; however, the tension they develop across the lower back to the glutes is very important for stabilizing the lumbar spine and pelvis. Also, the stored energy that occurs when the POS isn’t working, gets released during this motion and decreases the amount of work other muscles in the area have to do, making walking more efficient.

How can we target the posterior oblique sling in training? Well, we can do similar exercises that we would do for the anterior oblique sling, just change the stance. Here is a Cable Trunk Rotation using a POS Split Kneeling stance. Now, my inside leg is forward, making the concentric motion a POS motion, and not so much for the AOS.

As I mentioned earlier, the AOS and POS work in harmony. As one shortens, the other lengthens. This means that as one creates motion, the other controls the motion, ensuring that nothing goes wrong. As long as you have proper function in these two slings, you’ll have efficient force transfer and no pain.

However, what if they don’t work well at all?

The AOS and POS and Their Implications For Back Pain

Not all lower back pain is created equal. Some lower back pain (LBP) is caused by constant misuse, while other forms of LBP come from injury that then lead to misuse. In either event, LBP can present the same type of pain for an individual; however, it’s root cause may differ.

One thing will always be true with LBP, the deep muscles of the abdomen, like that transversus abdominis are dysfunctional. This is then coupled with a dysfunction of one or more of the body slings.

We only discussed the AOS and POS today. However, dysfunction in one or both of these systems can cause pain and inefficient movement. Many people with lower back pain only train their core or stretch, expecting this to be the final solution to their problems. The issue with this line of thinking is that it doesn’t appreciate the body as a series of complex systems working together.

The way the lumbo-pelvic region of your body interacts with the upper and lower body is paramount to creating a stable and risk-free environment for your body to operate. If these interactions are neglected, stability and efficiency decline, and dysfunction prevails.

So, if you have lower back pain and you’re not training through rotation, you might be missing the biggest gap that is restricting you from eliminating your pain!

Stay tuned for next week as we will discuss the other two body slings and take a deeper dive into all of their interactions. That way, we can solve your back pain for good!

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References

Anatomy Slings and Their Relationship to Low Back Pain. (n.d.). Retrieved September 07, 2020, from https://www.physio-pedia.com/Anatomy_Slings_and_Their_Relationship_to_Low_Back_Pain