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In my last blog post, The Thoracic Spine Domino Effect: Part 1, I discussed how poor thoracic spine function can come about and its potential for affecting other body systems via chain reactions due to its vast connections throughout the body; It can be compared to the first domino in a line of falling dominoes. We discussed the thoracic spine's contribution to prevention of injury to other areas of our body, optimal posture, and running performance. With this blog, I wanted to highlight the specifics of the thoracic spine's profound impact on other bodily systems including our respiratory, cardiovascular, and autonomic nervous systems.
The Thoracic Spine & Breathing
The thoracic spine heavily impacts our respiratory system and thus, breathing function. If you take a deep breath in, the lungs and ribs should expand out, the thoracic spine should extend, and the diaphragm should descend. This allows for a full and efficient inspiration or inhale. When fully exhaling, or emptying the lungs, the lungs and ribs should retract, the thoracic spine should flex, and the diaphragm should contract and raise up. Conversely, this allows for a full exhale, which is equally important (think: breathing out/getting rid of CO2 as waste) as having a good inhale of oxygen. If the thoracic spine and rib cage are stiff, our lungs and diaphragm may be restricted in their movements that help with both an inhale and exhale. As mentioned above, diaphragmatic excursion and dysfunctional breathing could result in poor functioning of our cardiovascular system, nervous system, and musculoskeletal system. This could negatively affect running economy and performance or could lead to poor recovery and decreased tissue healing. However, efficient diaphragmatic breathing is not as simple as you may think and unfortunately may not be “automatic.” Are you curious if you are breathing optimally and with proper mechanics? Check out this blog post by Dr. Kate, Breathing & Running, for some educational videos on how to perform diaphragmatic breathing most effectively.
How the Thoracic Spine Impacts Our Nervous System
One of the more commonly overlooked functions of the thoracic spine is its impact on our nervous system. The thoracic spine houses our spinal cord and its corresponding nerve roots that branch from the spinal cord. These nerve roots come together to form thoracic spinal nerves that supply many different areas of the body including the chest, arms, hand, abdomen, low back, and also aid in breathing. If these nerve roots become compressed, irritated, or damaged, pain or functional issues may arise.
The thoracic spine is also regionally very close to a large number of neurons, or nerve cells, within our autonomic nervous system (shown below), affecting both the sympathetic (“fight or flight”) and parasympathetic (“rest and digest”) components of this system. There is a sympathetic trunk, containing nerve cells linked to sympathetic nervous system function that runs parallel along either side of the thoracic spine.
There are also other nerves such as the Vagus nerve and Phrenic nerve, serving basic human functions that pass through the thorax near the thoracic spine. The Vagus nerve, our tenth cranial nerve, originates from the brainstem and travels through the neck and thorax. Some of its main functions within the parasympathetic nervous system include regulation of heart rate, blood pressure, respiration, and it even influences digestion and gut health. We can help improve and tap into our parasympathetic nervous system with mobilization of the thoracic spine due to its close proximity to these nerves. The more mobility that our thoracic spine has, the better we are able to perform deep, diaphragmatic breathing. As described by Dr. Melissa in her blog, What Happens in Vagus, Doesn't Stay in the Vagus, we are able to tap into the recovery functions of our Vagus Nerve and parasympathetic nervous system through diaphragmatic breathing. This can have HUGELY positive effects on our mental and physical resiliency as endurance athletes.
The thoracic spine can also contribute to adverse neural tension or neurodynamics. Neurodynamics refers to the mechanical and physiologic functions of our nerves. Healthy nerves have enough oxygen and fuel to serve their functions and can slide and stretch and move along with our other nearby tissues as our bodies go through different daily or athletic movements. Neural tension refers to poor movement or physiology of the nervous system, where nerves aren't moving freely with our body movements or they don’t have their basic requirements for healthy cells covered (e.g., not enough oxygen or fuel). For more information on neural tension, revisit Dr. Kacy's blog, What Is Neural Tension?, It is crucial for optimal nervous system health that we have adequate mobility, blood flow, and space throughout the length of the neural system. A common site of restriction of the neural system can be found at the thoracic spine due to its frequent lack of mobility. This can directly affect the nerves in this region and down the chain, which may create signs and symptoms of neural tension that can be improved with thoracic spine mobilization.
There are many crucial pieces of our nervous system that travel through the thorax and become affected by the function of the thoracic spine, creating a significant influence on our nervous system and vice versa. With this being said, if we do not focus on the function of our thoracic spine, it may affect our nervous system.
Cardiovascular System
The thoracic spine is also closely intertwined with our cardiovascular system. The thoracic spine and rib cage serve as bony protection for our heart, lungs, and large blood vessels. The thoracic spine vertebrae and rib cage together are stiff enough to provide adequate safe keeping for our most vital organs and vessels. On the contrary, it is also crucial that they have the ability to move well in order to carry out breathing in order for our cardiovascular system to function properly. The heart and lungs must work together to provide our body with oxygen-rich blood that it needs to operate. Without the necessary mobility of the thoracic spine and ribs, we may not be able to carry out full excursion of our diaphragm and lungs to help with oxygenation of our blood, which would also potentially create changes in on our blood pressure, heart rate, and more.
In summary, our thoracic spine mobility (or lack thereof) can affect so many different aspects of our body. Please refer to my previous blog post for some basic thoracic mobility exercises to begin with. My hope is that this blog series has motivated you to incorporate some thoracic mobility exercises and diaphragmatic breathing into your daily exercise routines for improving overall health, wellness, performance, and injury prevention!
Thanks for reading!
Dr. Allison Jones, PT, DPT