The Foundation of Movement
All of my previous movement-based articles have been leading to this: getting to the foundation of healthy, effective movement. You may have already guessed what this foundation is. If you said your core, specifically, the Inner Unit, then you would be right.
Because of the core’s importance to movement and health in general, the assessment I have new clients go through is almost entirely focused on core function and how the body relates to that function.
One can argue if core dysfunction has led to or been a catalyst for an injury, or if an injury leads to core dysfunction. Regardless, core dysfunction exists and it is more common than you may think. In more than 20 years I have not worked with a single client without some relevant level of core dysfunction, regardless of the reason they approached me.
Inner Unit (Core) Anatomy
The Inner Unit, as the image shows, consists of 4 separate muscles: Transverse Abdominis (TVA), Multifidus, Diaphragm and Pelvic Floor. These muscles securely attach the pelvis to the rib cage via the spine. A very important feature is that these muscles are under separate neurological control from other muscles making up the abdominal wall including rectus abdominis (6-pack muscles), external obliques, and portions of the internal obliques. Training the Inner Unit does not train these other muscles and vice versa.
The Inner Unit serves a number of purposes:
Stabilization & Lumbar Spine Decompression - The multifidus runs vertically along the spine and gives almost constant feedback as to the positioning of the vertebra relative to each other. The TVA resembles a corset with largely horizontal fibers running around the front and sides of the abdominal wall where it completes the loop via attachment to the thoracolumbar fascia.
When TVA contracts, it draws the abdominal wall inward from the front and sides towards the spine. This contraction increases intra-abdominal pressure. The pressure pushes down against the pelvic floor and up against the diaphragm. This pressure in opposing directions decompresses the lumbar spine by elongating or extending the spine. Consider the health and pain-relief implications of creating space between the vertebrae, taking pressure off of discs and nerves that pass through and/or exit at these joints.
Exercise Note* - The Inner Unit along with the ThoracoLumbar Fascia creates the body's own natural weight belt. When most people wear a weight belt, they will push outward against the belt to stabilize. This is a dangerous habit as it inhibits TVA contraction. Essentially you are saying it is not needed. Plus, it can lead to faulty motor programming and destabilize the spine when it is least wanted, such as when you are not wearing the artificial belt.
Foundation for Extremity Movement - The Inner Unit stabilizes the pelvis to the rib cage via the spine. The pelvis and the ribcage work together. You can’t stabilize one without the other. Before you move an arm or leg or even the head, the Inner Unit engages hundreds of milliseconds before movement. This occurs at a subconscious level—or at least it should.
Exercise Note* - If you are dealing with a faulty Inner Unit or poor posture, there is a high probability that spinal compression exists and nerve impingement is present. If a nerve is compressed, the conduction of information is suppressed. This can slow down engagement of the Inner Unit and inhibit stabilization of the pelvis and ribcage just enough to be a catalyst for injury as an extremity starts moving around a joint before that joint is properly stabilized. Consider the forces of compression, extension, shearing and torque which will not be properly managed and the effect it can have on joint/tissue health.
The Down Side of Pelvic and Rib Cage Instability
If the above is not enough to convince you that the Inner Unit is important, let’s consider the stabilization of the pelvis and rib cage from another perspective. In the image below we can see that the body is very intelligently designed. Take note that the lumbar spine as it rests between the pelvis and ribcage is meant to be stable. The body from the center outward alternates joint mobility and stability.
When I say that a joint(s) such as those of the lumbar spine are meant to be stable, it doesn't mean it is not supposed to move; rather it is not meant to be a movement initiator. For example:
The hip is meant to be mobile. If the body loses hip mobility, the joints above (lumbar) and below (knee) are asked to make up for that loss of mobility. From previous articles you should recognize that the knee, while a hinge, hates torque. Any more than 10 degrees of torque places great stress on the ligaments. Being knee dominant versus hip dominant when moving also places greater levels of shearing forces on the knee.
Poor hip mobility also impacts the lumbar spine. While some controlled lumbar motion is normal and acceptable, it should not be the initiator of motion. This happens more than we would like, and the result can be devastating. Just ask anyone with an acute or chronic lumbar injury, especially to the most injured joint in the spine, L5S1. Coincidence? I don’t think so.
The Thoracic spine is meant to be mobile. It is where most spinal rotation should occur along with extension. If there is thoracic restriction, which is very common, the lumbar spine is asked to pick up the slack along with the cervical spine and shoulder joints. If you have both hip and thoracic mobility issues, the lumbar spine is attacked from both above and below. With thoracic restriction, performing overhead movements is more harmful and if you have to perform a throwing activity, you can literally “throw your arm out” as your body attempts to compensate.
Can you see a pattern developing? Is the picture coming into focus?
Let’s take a closer look at the lower body and what can happen when the pelvis is unstable.
The primary function of the glute muscle complex is to control the hip joint; that is, the movement of the femur (thigh) around the pelvis. Whether you are walking, running, climbing stairs, jumping, squatting, lunging etc. the hip plays a pivotal role.
The more challenging the movement, the more power and control required from the hip. The glutes can create a great amount of power and leverage if—IF—they have a foundation to work from. For the glutes to be successful, the pelvis has to be stable. If it moves it has to move in sync with other aspects of the body. If the pelvis is unstable, the femur is unstable and energy is wasted. Here is an image of two extremes in the landing phase of a single leg exercise or transitioning from one leg to another, such as walking or running or even going down the stairs.
On the left is a good landing phase. The pelvis is stable, so the glutes can control the femur. The hip, knee, and ankle align vertically. The energy of impact can travel vertically through the body and be dissipated.
On the right is a common cascade effect due to an unstable pelvis resulting from poor Inner Unit function. Upon landing the pelvis moves along with the femur. Pelvic instability prevents the glutes from properly controlling the position of the femur, resulting in femoral internal rotation. This places increased torque along with shearing forces on the knee. To minimize the risk of knee injury, the body allows the ankle to pronate or collapse inward along with a flattening of the arch. The energy of impact is poorly controlled if at all and the body has no choice but to initiate split second decisions as to how to dissipate that energy while reducing the risk of joint trauma to any or all involved.
Consider that image of pelvic instability. Is it any wonder we have so many adults and even teenagers dealing with acute or unresolved chronic leg joint and tissue problems? Consider the damage if you have pelvic instability yet perform highly repetitive gait pattern activities. Walking can be bad enough; just add the impact of 3 to 7 times your bodyweight being transferred through the body upon every step when running.
Similar scenarios can be created for the upper extremities except it is the rib cage that is the foundation attachment point. When it comes to unresolved joint/tissue challenges or training to optimize your performance at a given sport or activity, everything your body does or doesn’t do is for a reason. When your body responds in a manner that is in opposition to your best intentions and efforts in spite of them being realistic, it is likely time to dig deeper to uncover the root causal factor.
Time and time again, I uncover Inner Unit dysfunction. And while similar dysfunction exists in so many individuals, the manner in which it manifests outwardly, the symptoms and the challenges, can vary greatly.
Whatever you do, don’t give up. At the same time consider that a comprehensive movement and core assessment may be in order. If you have any questions, just ask. I will gladly assist if at all possible.