Before getting into this month’s newsletter, I need to inform you of my naming these newsletters “THE MYOMEMORY” BULLETIN.”
Now to this month’s newsletter titled “Asymmetry.” Humans are inherently born asymmetrical when describing our anatomy and structure. The structure and location of our digestive, respiratory, and cardiovascular systems make us naturally asymmetrical to some degree. That is because we have a liver on the right side that weights approximately three to four pounds and on the opposite side we have a spleen weighing less than a pound. In addition, we have three lobes for the lung on the right and only two on the left. Also in our upper trunk, we have a heart that lies more to the left.
It is this organ asymmetry just mentioned, coupled with how our nervous system including the peripheral and central nervous systems reacts to the vertical forces of gravity and ground reaction force (GRF) of our environment which is also involved with the creating asymmetry. Additionally, our foundational neurodevelopmental reflexes, vestibular imbalances, and patterns of dominance play a role in the integrated asymmetry of our anatomy and structure.
The end result of these tendencies is the human nervous system to stand reflexively on the right leg and rotate the body and trunk to the left in reaction to GRF during the pinnacle of our human posture and movement, a cross-patterned gait. It is therefore no wonder researchers have found most people bear more weight on their right dominant leg, causing it to be nearly 5% larger in volume! Overtime, uneven loading of a dominant leg may result in leg-length discrepancies, pelvic bowl rotations, spinal compensations, and more important musculoskeletal pain and other symptoms.
These asymmetries not only come from standing, but also sitting. Think about how someone shifts their weight onto the right ischial tuberosity and hip when reaching with the right arm while sitting causing the rib cage and trunk to rotate to the right to maintain postural stability. Couple that with the numbers that the average person in the United States spends 54.9% of their monitored time, or 7.7 hours/day in sedentary positions and you can see how these factors play into the inherent, asymmetrical anatomy and structure of humans.
On top of that, take into consideration that the majority of us in the United States are right hand dominant, whereas left hand dominance comprises approximately 10-12% of the general population. Right handedness therefore reinforces this typical right leg dominant pattern of your neuromyofascial system to where you stand on your right leg and rotate your body and trunk to the left. That pattern is also reinforced with being vestibular dominant on the left side and having right eye dominance. But whether you are standing or sitting, the upper torso rotation needs to be balanced in order to function in this environment of gravity and GRF let alone to optimally breathe. Remember that breathing is our most foundational movement pattern and also the most dysfunctional according to Dr. Karl Lewit, M.D.
This neuromyfascial right leg dominant pattern in standing just mentioned is part of how you walk (gait), run, and stair climb. It is this repetitive dominance of one side of your body over the other that over time creates a structural and muscle imbalance throughout your body causing the inefficient alignment and movement of your joints.
The human brain inherently acquired this dominant cross-over pattern as your nervous system matured and developed such that each side of the body communicates with the opposite brain hemisphere. Therefore, almost all sensory-motor functions on the R side of the body are either realized or controlled in the L brain hemisphere and vice versa as seen with your cross-patterned gait.
But no matter the cause of these asymmetries, they usually can be found at the root of musculoskeletal pain and other symptoms. With M.A.T., I recognize these asymmetries and attempt to minimize their affects on your musculoskeletal system in order to optimize your body’s functional mechanics and prevent serious pain issues and other symptoms as your body gets older.
During the M.A.T. evaluation process I do with every client, I am looking for these asymmetries and the resulting muscle imbalances or neuromyofascial imbalances as I refer to them in M.A.T. as soon as someone enters my clinic. In addition, I look for postural and functional compensations from “ideal skeletal alignment” such as a loss of cross-patterned gait, upper and lower crossed syndromes, and an unleveled pelvis or head.
With the M.A.T. evaluation I do each visit, I look at someone’s structural alignment standing, sitting, and supine (on your back) looking for visible asymmetries which give me clues suggesting areas of soft tissue tightness or weakness as well as structural abnormalities, like a long leg on one side. Again because most people are right side dominant I expect to see some typical findings like the right foot is turned out more, the right shoulder is lower and protracted, an upper body shift on the right, and a pelvic-hip shift on the left.
In standing and sitting, I am always looking at the client from the front and back as well as from the side to reveal their imbalances visually scanning their structure from the feet up and the head down. After performing a complete M.A.T. assessment in standing and sitting, I have a general sense of possible areas of tightness or weakness. However, checking for asymmetries doesn’t stop there. I continue to assess my client on the table in supine as I begin their treatment.
With the client on the table, I am not only looking visually for asymmetries and neuromyofascial imbalances, but also feeling their soft tissues and noting how the client’s body responds to both active and passive movement. In addition, I am looking for a leg length discrepancy. Leg length discrepancies, or as it has been alternatively termed, “the short leg syndrome,” is by far the most important postural asymmetry according to Erik Dalton and his “Myoskeletal Techniques.”
In the osteopathic method of musculoskeletal assessment, ART is an acronym they use which stands for:
•Asymmetry
•Restriction of motion
•Tissue texture abnormalities
Because the osteopathic ideology played a significant role in my early career working at Heights General Hospital in Albuquerque, I am always thinking about ART as I evaluate a client’s alignment and structure with each session.
Where there is structural asymmetry, you will usually find a neuromyofascial imbalance which is due to a combination of weakness and hypertonicity or tightness. Your voluntary skeletal muscle system which by the way is the largest organ of your body, measures in at over 40% of your body weight and is maintained in a state of balance and coordination throughout a wide range of postures and movements with a triad of sensory input including vestibular, visual, and proprioceptive.
Your muscles, therefore, are at once the source and recipient of the greatest neural activity from the peripheral and CNS in your body. That includes sensory and motor activity, segmental and cerebral pathways, plus autonomic activity in relationship to the metabolic, visceral, and circulatory demands required during human posture and movement. A neuromyofascial imbalance brings us back to the human nervous system which is at the core of all human activity and survival.
Initially in your neurodevelopment, these neuromyofascial imbalances were created predominately by your visual and vestibular sensory input involving primitive reflex activity and the so called “righting reflexes” that stay with you throughout your life as the foundation to your posture and movement. However as your nervous system matured, visual and proprioceptive sensory input in reaction to GRF dominated allowing you to develop as mentioned, a pinnacle of human posture and movement, a cross-patterned gait.
Proprioception or kinesthesia, is the sense that lets you perceive the location, movement, and action of your body against the vertical forces of gravity and GRF. It encompasses a network of sensations, including perception of joint position and motion, muscle force, and effort. These sensations arise from signals of sensory nerve receptors of the peripheral nervous system in the muscles, skin, joints, and from signals related to motor output. It is with proprioception that allows you to judge your upper and lower extremity limb positions and motions, force, heaviness, and stiffness, and viscosity (thickness).
Two proprioceptors or sensory organs at the local level that are instrumental in this process and are vital to the functioning of your neuromyofascial system are the muscle spindle (MS) and golgi tendon organ (GTO). These two neuromuscular sensory receptors located in the muscle-tendon complex of every skeletal muscle in which there are over 300 on each side of your body, affect your skeletal equilibrium, balance, stability, mobility, posture, and movement.
Simply, both these proprioceptors are primarily responsible for regulating or setting the isolated myofascial tone, stiffness of your neuromyofascial system determining how your isolated joints will respond to the vertical forces of gravity and GRF. Although the GTO’s and other sensory systems contribute to proprioception mainly through the vestibular system in response to gravity, the muscle spindles are considered the most important of the neuromyofasical system in its response to GRF.
They are like a motor generating power and subsequent movement against GRF. That is because the muscle spindles indicate the degree to which the muscle needs to be activated in order to overcome the vertical force of GRF. It is actually the stretch reflex of these muscle spindles in the lower extremity myofascia reacting to GRF that facilitate muscles of the lower extremity kinetic chain to generate enough power to allow you to move against this vertical and external force as seen with your cross-patterned gait.
In fact, muscle spindles are the most readily found proprioceptive, local sense organ in skeletal muscles. Rough estimates have suggested approximately 50,000 muscle spindles are in the entire body. The muscle spindle is actually a stretch receptor having its own motor supply consisting of several “intrafusal” muscle fibers whereas the individual, power producing fibers of the muscle enclosed by the “myofascia” are called the “extrafusal” fibers.
When a muscle spindle’s associated muscle is stretched, the spindle can cause two things to happen:
1) It may signal its associated muscle to contract in order to prevent it from stretching too far and too quickly with the goal of protecting that isolated muscle.
This stimulation of a reflexive muscle contraction is known as the the stretch or “myotonic, stretch reflex.” Remember the patellar reflex done with a reflex hammer at the doctors office? That is an example of the myotonic, stretch reflex.
2) It can cause inhibition of the opposing muscle or its antagonist to the muscle being stretched so as to prevent it from contracting and inhibiting any further stretching which is referred to as “reciprocal inhibition.” It is reciprocal inhibition that is foundational to your functional movement.
Ultimately, it is the muscle spindle that alerts the brain of nearby joints and the soft tissues that are in danger of being stretched too far. This is a very important concept in understanding the sense of body awareness also known as proprioception or kinesthetic awareness. Because the muscle spindles indicate the degree to which a muscle must be activated in order to overcome a given resistance such as GRF, as a load increases, the muscle and its myofascia get stretched to a greater degree creating more power. This process causes engagement of the muscle spindles for that muscle resulting in greater activation, facilitation, and tension of the host muscle.
Skeletal muscles of the human body that perform precise movements will have many spindles per unit of mass to help the exact and precise control of contractile activity. For example, the sub occipital muscles have approximately 36 spindles per gram of muscle tissue whereas, the much larger gluteus maximus has less than 1 spindle per gram of tissue.
During the functional activity of walking, the muscle spindle is responsible for the “eccentric or lengthening muscle loading” causing pronation of the lower extremity kinetic chain in response to GRF followed by the “concentric or shortening muscle contraction” causing supination to generate the power to overcome the force of gravity and GRF at push off.
The GTO, on the other hand, lies in series with the extrafusal fibers of a skeletal muscle and does not have its own motor innervation as was seen with the spindles and their intrafusal fibers. They are inhibited and facilitated by reflexes involving the vestibular, visual, and proprioceptive sensory input. Their function is to send tensile force information to the spinal cord and brain and specific neurons receiving input from the vestibular and visual sensory input specifying the amount of tension that a muscle should produce in creating skeletal equilibrium and balance.
If that tensile force level exceeds this set point, dependent upon the location of your integrated, body COG, some of the motor neurons innervating a muscle will be inhibited at the local level which in turn lowers the force produced unless some other nervous system signal from the higher centers of the brain inhibits or cancels it out.
GTO’s again are proprioceptors providing output information that encodes the level of a tensile load applied to a tendon. For this reason, the GTO’s and particularly the extensors of the lower extremity kinetic chain, are critical in sensing the forces exerted to resist imposed loads like the force of gravity and GRF acting on your body. This can cause a reflex of inhibition to the muscle. As a result, the reflex action of the GTO is referred to as an “inverse stretch reflex” rather than the “myotonic stretch reflex” as seen with the MS and is referred to as “autogenic inhibition.”
As you can see, GTO’s are sensitive to tension changes and rate of change within a muscle because they are located at the musculotendinous junctions. They are responsible for sending information to the brain especially when they sense a tensile force overload. However again, both of these proprioceptors, the MS and GTO, at the local level are primarily responsible for reflexively setting the stiffness of the neuromyofasical system in its response to the vertical forces of gravity and GRF. Keep in mind though that there are many other proprioceptors such as in the ligaments of joints that affect the function of theneuromyofascial system which will be a topic of another newsletter.
The neuromyofascial imbalances I find during the M.A.T. evaluation process are the result of neuromyofascial reflexes involving the MS’s and GTO’s and “reciprocal and autogenic inhibition.” The major role of the myotonic stretch reflex and reciprocal inhibition is the maintenance of your posture. For example, if you are standing upright and start to sway to the left, the muscle in the legs and torso are stretched, activating the myotonic reflex and reciprocal inhibition to counteract the sway. The neuromyofascial system and the joints of the body are controlled by two opposing sets of muscles which must work in synergy. Thus, when a muscle spindle is stretched and the stretch reflex is facilitated, the opposing muscle group must be inhibited to prevent it from working against the resulting the muscle contracting.
With the GTO and autogenic inhibition, it is now believed it is does more than just protect the muscle from tensile overload. It has been found that the GTO is extensively involved in motor control spreading the amount of work evenly across the entire muscle, so that all motor units are working efficiently. That is, if some muscle fibers are doing more of the work, their GTO’s will be more active, which will tend to inhibit the contraction of those muscle fibers. As a result, other muscle fibers that are less active will have to contract more to pick up the slack, thereby sharing the work load more efficiently.
However, it is the combination of sensory input from your visual, vestibular, and proprioceptive systems of your nervous system all working together in synergy that actually generates your posture and movement whether standing or sitting. This triad of sensory information sent to your brain in regards to gravity and GRF is integrated and processed in certain localities of your brain causing the motor nerves to your muscles to respond in creation of your vertical integration, orientation, equilibrium, balance, stability, and mobility, posture, and movement in the performance of your everyday, physical and functional activities.
Whether standing, sitting, walking, and running, your vertical, skeletal equilibrium, balance, stability, and mobility is the key to your survival and function in this environment of gravity and GRF. Equilibrium, balance, stability, and mobility while being vertical describes this interplay, this dynamic dance which is your response to gravity and GRF no matter the physical activity generating your posture and movement. But, it is not a fixed state of alignment, but rather a never-ending series of fine, subtle adjustments occurring throughout your body in response to these vertical forces of gravity and GRF.
When this dynamic polarity of skeletal equilibrium, balance, stability and mobility is managed successfully by your peripheral and CNS, then you can successfully integrate and orient yourself to your constant environment of gravity and GRF. You can live because “motion is life!”
In my next edition of the “THE MYOMEMORY BULLETIN”, I will discuss other proprioceptors involved with your skeletal equilibrium, balance, stability, and mobility. Until then, “BE WELL!”