PT on the Net Research

Scientific Balance Training - Part 4B


A Note from Paul Chek: Welcome to Part 4B of Scientific Balance Training. I realize this series has been more technical than many would have expected to read in an article on balance training. However, I specifically did not water this article series down for a couple reasons:

  1. I believe in “up-educating.” When people have to look up unfamiliar words in the dictionary or stop reading to get out an anatomy book, they will develop new neuronal pathways and expand their awareness of the incredible complexity of the human body. By doing this, you will become even more aware of the responsibility bestowed upon you as an exercise professional!
  2. Based upon the feedback letters I get, there are a significant number of physiotherapists, osteopaths, chiropractors and medical doctors now reading my articles on PTontheNET.com. Because of this, I feel it is important to share articles that are in a format that is encouraging to them as well. Many medical professionals may have found these articles on the upper cervical spine particularly applicable to their clinical practice, as the atlas subluxation complex is likely to be both the most common, and the most commonly overlooked subluxation of the spinal column due to the fact that the atlas has the least ligamentous support and greatest range of motion of all spinal vertebra, as well as being atop the most flexible portion of the spinal column. In addition, the head, which represents approximately eight percent of body mass, rides upon this flexible column, making subluxation of the atlas comparatively easy in consideration of the mechanical challenges faced by this region of the body during contact sports, intrinsic loading during unilateral lifts and of course, auto accidents.

Without further ado, we begin where we left off in Part 4A. Proceed with text book and vigor!

Grostic proposed the hypothesis that the ASC could embarrass function in tracts of the lateral and ventrolateral columns by virtue of the dentate ligaments. The dentate ligaments are an extension of the pia mater and consist of collagen and elastin fibers. With the first attachment at the foramen magnum and the last at T12-L1, there are approximately 21 of these triangular ligaments. Arising continuously along the spinal cord between the ventral and dorsal roots, they impale the arachnoid membrane, inserting themselves to the dura between the spinal nerve roots.

The dentate ligament provides important fixation for the spinal cord and, with assistance from the cerebrospinal fluid, protects the cord from sudden shocks and displacements. Dentates of the upper cervical region are short and thick, stronger than those caudal to them, and pass almost perpendicularly to their attachments on the dura mater. Their orientation is such that they would limit vertical movement of the cord.

The spinal dura mater is generally understood to be attached to the edge of the foramen magnum and to the posterior surfaces of the second and third cervical vertebral bodies, with fibrous slips to the posterior longitudinal ligament, especially toward the caudal end of the vertebral canal. In contradiction to Grays Anatomy, Grostic refers to cadaver studies in which he identified numerous strong attachments of the dura mater to both the lateral masses and posterior arch of the atlas. The significance of Grostic's finding is that any subluxation of the atlas, by virtue of dural attachment, could transfer the forces of eccentric motion into the cord via the stronger cervical denticulate ligaments.

The dentate ligaments, as shown by Breig, are strong enough to distort the spinal cord and fold its peripheral blood vessels, when under the load of extreme flexion or extension postures. Grostic found the average lateral atlas subluxation to be three degrees in a retrospective study of 523 patients. He then calculated this as equivalent to a three millimeter condylar shift of atlas on axis. Calculated at its widest point, the average adult cervical spinal cord diameter is 12.1 millimeters. This would indicate that if the dentate ligaments were rigid, the average atlas subluxation could potentially distort the cord by 24.8 percent of its natural diameter.

Although the dentates are not rigid, Kahn refers to anatomy professor Rollo McCotter, who suggested that dentate ligaments and their attachments might increase in strength and size after subjection to a long period of abnormal stress. He also indicated that this type of ligamentous change is common in orthopedic conditions. Nonphysiological hypertrophy of the dentate ligaments could undoubtedly increase their ability to distort the cord under aberrant biomechanical conditions.

The relationship between the bony structure of the atlas, the dens of the axis and the spinal cord, and the “free zone” for the spinal cord to move has been broken into thirds, which are considered to be an anatomical constant. One third is occupied by the dens (a), one third by the spinal cord (b) and the remaining third by the free space (c + c)."

Based on Steele's law of thirds (above), the average three millimeter atlas subluxation would be a 42 percent distortion of the cord's necessary static and dynamic physiological space. In the situation of cervical side bending, where coupled motion of the upper cervical spine dictates that C0 and C2 make opposite rotations in the midst of ipsilateral translation of C1, it becomes evident that C0-C1-C2, during both the coupled and eccentric motions of subluxation, could stress the cord. This stress would occur through the mechanical linkage of vertebra-dura-dentate as described above and is demonstrated below.

Image above: Speculation about the potential stress exerted on the cord through dentate ligaments, by subluxation of atlas into right frontal plane (as patient attempts a cranial-cervical side bend right). A. Traction of left superior dentate ligament on the cord, as right side bending occurs. B. Traction of second dentate ligament (right), resulting from lateral subluxation of atlas, as well as physiological movement of atlas during right side bending. C. Concomitant right rotation of axis occurs in conjunction with motion of right side bending, which may contribute to traction forces on cord through eccentric motion, as occurs with subluxation. D. Dentate ligament at C3 level. E. Spinal cord. Arrows pointing away from each other, cord distention, arrows pointing toward each other, cord compression.

The significance of this condition to posture and balance becomes evident when considering the cord tracts to be stressed via location of the dentate ligaments. They are the dorsal and ventral spinocerebellar, corticospinal and spinothalamic (below). Breig states that tension set up in the brain, spinal cord, and nerve roots, through the presence of a pathological structure or lesion located within or outside the tissue, is a prominent cause of neurological signs and symptoms. He also implies that when nerve tissue is bent, stretched or "under traction-torsion as described above," the molecules of its membrane are drawn further apart on its convex than on its concave aspect. This unequal separation will result in a difference in osmotic permeability and hence, in the resistance of the membrane to ionic migration.In turn, this will probably result in alterations of the axon potentials. A simple example of how axonal deformation alters axonal potentials in the loss of sensory and motor function often results from simply falling asleep on your arm. You wake up with a sensory loss, and for a time, the arm displays loss of motor function.

Image above: A. Proximity of the dentate ligaments to peripheral cord tracts is such that abnormal tension on dentate ligaments may distort their form and function. Lateral subluxation of atlas, through dentate ligaments, may create longitudinal tensile stress in cord, as demonstrated here. B. Torsional stress in posterolateral and anterolateral areas of cord. This may be the case during the coupled motions of cranial side bending where there is rotation of C2 with ipsilateral translation of atlas.

The spinocerebellar tracts are located at the periphery of the cord, with the lateral corticospinal and lateral spinothalamic tracts adjacent to them. These tracts, located in the immediate vicinity of the dentate ligaments, are therefore "potentially" subject to maximal irritation by traction placed on them.

Both ventral and dorsal spinocerebellar tracts subserve largely the hind limb and trunk areas, with functions for the forelimb and neck also present. These tracts convey information largely from muscle spindles and tendon organs about joint position as well as touch, pressure, and pain information from the skin.

In the lateral corticospinal tract, there is a somatotopic arrangement, with lower limb fibers running on the periphery and those for the trunk and the arm lying deeper. Most fibers end on interneurons, which transmit the impulses for voluntary movement to anterior horn cells, and transmit cortical inhibition via interneurons.

The lateral spinothalamic tract is the pathway for pain and temperature sensation as well as extero and proprioceptive impulses. It is divided somatotopically - the sacral and lumbar fibers lie dorsolaterally, and the thoracic and cervical fibers lie ventromedially. Fibers for pain sensation probably lie superficially, whereas those for temperature sensation lie deeper.

Owing to mechanisms common to cord stress as described by Breig, it seems logical that aberration of afferent impulses in the dorsal and ventral spinocerebellar tracts could distort the comparator functions of the cerebellum. These functions are vital to coordinated movement. With experimental lesions to the pyramidal tract, there is a loss of accuracy in reaching for and grasping objects, and during gait the affected extremities are held slightly too adducted and over flexed. This could be considered a dynamic postural insult and these people are likely to be challenged by typical Swiss ball and balance board type activities used in the gym!

Because the corticospinal motor system (pyramidal) is intimate with the extrapyramidal system, which is primarily concerned with more basic gross motor control activities related to attaining and maintaining posture, alteration of corticospinal efferent impulses could disturb postural balance. As I have implied repeatedly, in general any form of postural disorder is antagonistic to developing optimal balance skills or motor skills.

The lateral spinothalamic tract is somatotopically organized in a lateral to medial organization, i.e. sacral-lumbar-trunk-cervical. This organization would likely encourage irritation of the sacral and lumbar regions, especially in the case of distension through the dentate ligaments. Such aggravation in this tract may be responsible for low back and leg pain, as proposed by Grostic. The relevance of low back and leg pain to craniofacial and cervical pain becomes evident in patients who develop craniofacial and cervical symptoms secondarily. Patients who demonstrate subclinical (asymptomatic) craniofacial, cervical or even shoulder/arm symptoms, may have become clinical (with pain) through summation of back and/or leg pain.

Many patients experiencing both craniocervical and low back pain can be effectively treated; their symptoms are often alleviated by correction of upper cervical subluxation and posture. Empirical evidence that back pain, or pain of any other origin, may precipitate craniofacial pain (or vice versa) can be seen when any ganglion or nerve root carrying nociceptive impulses from a seemingly unrelated situation is anesthetized. For diagnostic purposes an anesthetic can be applied to the pterygopalatine (sphenopalatine) ganglion (particularly effective in those with allergies!). On activation of the anesthetic, the patient’s back pain, foot pain, headache, and other seemingly unrelated conditions were often alleviated. Relief from this procedure often far outlasted the duration of the anesthetic agent. The same can be seen with diagnostic injections into the carpel and tarsal tunnels, at the radial nerve, and seemingly unrelated trigger points.

A plausible explanation lies in known physiological laws. Any person who has experienced craniofacial and/or neck pain as a result of whiplash, stomatognathic disharmony, or other related malady, is very likely to have developed facilitated nervous pathways. The Law of Facilitation states: when an impulse passes through a certain set of neurons to the exclusion of others, it will take the same course on future occasions, and each time it traverses this path the resistance will be smaller.

In the case of the ASC for instance, where both altered postures and nerve function could result in back pain, the law of radiation may come into effect. This law was developed in the 1800s by a physiologist named Pfluger and states: If the excitation continues to increase, it is propagated upward, and reactions take place through centrifugal nerves coming from the cord segments higher up. This upward propagation would likely find the facilitated pathways just as water always finds the easiest way downhill.

These laws may help explain why patients with pain anywhere caudal (distal) to the craniofacial region may have exacerbations of old, seemingly unrelated head pain. It can also be speculated that the application of an anesthetic to any ganglion or nerve branch conveying noxious impulses, whether it is induced by allergy (pterygopalatine ganglion) or orthopedic insult (tarsal tunnel), would decrease the algebraic sum of noxious impulses reaching the cord. This would explain the alleviation of headaches and seemingly unrelated pains by such procedures. The fact that the nervous system summates pain could also explain many of the short-term therapeutic benefits demonstrated by any number of treatment approaches such as massage, acupuncture, chiropractic, exercise, kinesiological manipulation and muscle activation techniques aimed at seemingly local disorders. All of these techniques manipulate and modulate sensory–motor input and may serve to lower the total sum of noxious inputs to the cord for a given period of time.

Compensatory Shifts of the Center of Gravity of the Head and Pelvis to Maintain Stability

Our body achieves maximum stability when our center of gravity of all our weight bearing segments lie in a vertical line and are centered over our base of support. When one segment becomes out of line, a compensatory malalignment of another segment occurs to maintain a balanced position of the body as a whole.

Through experiments by Seemann, the center of gravity of the head was discovered to be located slightly above the auditory meatus on a horizontal line at the midsagittal plane of the head. The center of gravity of the body lies in the midsagittal plane and somewhat anterior to the upper sacral spine. It is reported to be 4cm in front of the first sacral vertebra in the standing anatomic position.

Studies using objective measurements to determine the relationship between atlas laterally (lateral displacement) and pelvic shifts into the frontal plane have been conducted by both Cripe and Seemann. Seemann also recorded the relationship between atlas rotation and pelvic distortions into the transverse plane. In both studies, objective measurements were obtained through X-ray and by Anatometer, a machine specifically designed for measuring spinal and pelvic distortion.

In Seemann's study of 355 patients, there was a perfect relationship between C1 laterally reducing toward zero and pelvic distortion in the frontal plane (a low ilium) reducing toward zero. There was also a 99 percent relationship between C1 rotation reducing toward zero and pelvic distortions in the transverse plane reducing toward zero.

Cripe hypothesizes that as the center of gravity of the skull shifts into the left frontal plane, the contralateral iliac crest will lower (tilting toward the opposite frontal plane). His hypothesis was found to be correct in 27 of 33 cases (81.8%). Of the remaining six cases, three were attributed to their unusual case histories, and three were unexplainable. Other sources of pain can alter the physiological response, clouding the clinical picture as described above.

The relevance of these observations lies in the body's inherent desire to maintain a stable base. As the head moves into the left frontal plane, the body will bear more weight on the ipsilateral leg. By doing so, the center of gravity of the body moves under the center of gravity of the laterally tilted head (below). This can be observed by standing on one leg and noticing the body's movement in relation to a stationary object. Clinically, I have noticed that clients with lateral or rotational subluxation of the atlas tend to fall off such implements as Swiss balls, balance boards and balance beams, usually in the same direction. Running and strength athletes presenting with an ASC have a higher incidence of injury to the same side of the body, such as multiple left knee or left ankle injuries.

The postural changes shown here concurrent with the ASC are synonymous with functional scoliosis and require compensation at all spinal levels. These spinal compensations, left untreated in the adolescent, could potentially lead to structural scoliosis as he or she passes through puberty. As evidenced in figures B-D above, multiple mechanisms exist by which musculoskeletal and visceral pain as well as poor posture and poor balance may arise.

All indicators of these studies suggest that the body, whether in the upper cervical or pelvic region, naturally gravitates to its most stable position. As indicated in the preceding sections of this article series, this would ideally be anatomical neutral, yet due to survival reflexes oriented around the vital sense organs, the body will seek the most stable position while trying to maintain ideal head position.

Part 4B Summary

Congratulations for finishing Part IVB of Scientific Balance Training. The take-home points from this article include:

  1. The spinal cord is supported within the spinal column by the dentate ligaments. The dentate ligaments have been found to attach at the atlas and have been shown to hypertrophy, becoming stronger when stressed. Any subluxation of the ASC will stress the dentate ligaments, potentially making them stronger and less elastic over time, thus increasing their potential to distort the spinal cord. Distortion of the cord is a real likelihood, because as shown by Grostic in his retrospective study of 523 patients, the average lateral atlas subluxation was three degrees, which equates to a three millimeter lateral translation. With the upper dentate ligaments being strong enough to distort the cord and fold it’s peripheral vessels, as shown by the famous neurosurgeon Dr. Breig, there becomes a clear mechanism to explain the myriad of symptoms presented by such patients, of which balance problems are often inclusive! I referred to “Steele’s Law of Thirds” in the article. This law states that in the normal human atlas and foramen magnum, the space taken up by the cord is about a third the total space in the canal at C0/C1, which by design, leaves adequate room for the cord to move relatively unimpeded during physiological movements of the head/neck complex. Clinically, it can be seen that in the presence of the ASC, Steels’s Law of Thirds is broken due to potential engorgement of the cord by strangulation of peripheral vessels feeding the cord as well as by lateral displacement secondary to atlas or axis subluxation. Such subluxation causing nonphysiological cord tension, cord compression and interruption of normal physiological motion within the spinal canal. It is theorized that this cord tension overflows into the brain stem as well.
  2. Due to the anatomical location of the dentate ligaments relative to the underlying cord tracts, subluxation causes interruption of normal neuronal conductivity. Clinically, I see this as excitation of some muscles and inhibition of others, creating a cloudy clinical picture, which such patients commonly suffering repeated re-injury and/or an ongoing string of injuries that seem to have no logical sequence to them. Such injuries can be deemed secondary to decompensation and, the harder the more mechanical stress such individuals endure, the sooner they usually experience pain and dysfunction in concert with reduced athletic performance. If you recall the third image above, where it showed the somatotopic organization of the cord tracts underlying the dentate ligaments at their point of origin from the cord, you will see an interesting pattern emerge. In both the proprioceptive tracts (spinocerebellar) and motor tracts (pyramidal or corticospinal), the somatotopic arrangement is such that the tracts to first be effected by cord distortion are those controlling the sacral, lumbar and thoracic regions. Having treated no less than 500 such cases, it has been my experience that this is why so many people with the ASC seek help from medical professionals for back pain, yet don’t experience cervical pain initially - generally, it can take up to five years for some of the people with small deviations/subluxations of the atlas/axis complex to develop neck pain. Now, with regard to balance and the implementation of balance training, please note that the pyramidal tracts (also known as the corticospinal tracts) are in very close proximity to the dentate ligaments. As I pointed out in the article, “Interruption of corticospinal fibers at or below its cortical origin causes impairment of movement in the opposite body-half, especially severe in the arm and leg; characterized by muscular weakness, spasticity and hyperreflexia and a loss of discrete finger and hand movements. ” In review of the neuroanatomy here, I think you can clearly see that any distortion of the corticospinal tracts could cause balance and general motor control challenges. What I would like to point out here is that these people, having any number of potential subluxation patterns in any variety of degrees of severity, will present “functional impairments” of the sensory-motor system. This means that they are often seen as “normal” by those not trained to recognize or correct the ASC. My files are rife with such cases! These are the people that seem to be more challenged than most to sit on a Swiss ball or to sit on it and lift one food for example. They are the people that, even after months of training, seem to be challenged by lunging, or moving and catching a medicine ball - they are often the people that can talk for hours about their frustration with having to been to many doctors and therapists trying to get over the musculoskeletal complaints!
  3. Finally, in the last image above, Figure A shows a posterior view of a person with normal anatomical relationships, yet in Figure B, you can see the classic functional scoliosis that results from an atlas/axis subluxation. As demonstrated by Dr. Cripe’s studies, the greatest majority of people will demonstrate a weight shift, moving their pelvis under the displaced head in attempt to improve stability in the gravitational field. Clearly, such compensation will predispose these individuals to overuse syndromes, particularly in the leg they have shifted to and the low back. For those of you without the extensive training I offer in the third year of my C.H.E.K Certification program, you can identify those of your clientele that may need upper cervical assessment and correction by a trained professional by simply looking at the orientation of the client’s head on their neck. For example, a horizontal line drawn through the eyes at pupil level should be perpendicular to the vertical axis of the body, while a line from the point directly between the eyes and through the dimple of the chin should be true to vertical. Compare Figures A and B to see normal (A) and abnormal (B). Finally, anyone placed on bilateral, calibrated scales should not exhibit a weight shift of greater than five pounds from left to right at any time. A general rule of thumb is that where there is an ASC, the greater the weight shift, the greater the subluxation and the worse their balance is likely to be relative to their true balance potential! It is worth noting that these people will commonly develop muscle imbalances as a byproduct of resistance training. This is because the cord tracts are imbalanced with regard to inhibition and excitation, and the result is asymmetrical distribution of load, or load sharing, throughout the body. While they may get stronger and appear to be improving their physique, the ability to generate greater and greater intrinsic forces in the presence of such neurological mayhem only facilitates progressive derangement of any and all joints being controlled by the muscles fed by such inept neurological pathways.

While I can’t begin to teach correction of such a neuromechanical challenge through an article series due to extensive preparatory training that is required and the tremendous professional responsibility that goes with making such corrections, the goal I seek to accomplish by educating you as I have here is to empower you to be better able to identify those that are at risk with balance training in today’s “let’s make exercise fun environment! By looking at posture and anatomical orientation as here described, in concert with the use of bilateral scales, you can easily weed out your high-risk clients and seek to find professional help for them - a gesture that is best offered in the prodromal stage (before they are injured). In my experience of evaluating and treating such upper cervical corrections, I have found the best and most qualified are those chiropractors certified or trained by the National Upper Cervical Chiropractic Association (NUCCA). While many others will attempt to make upper cervical corrections, you will always know if they have accomplished the objective by looking at the anatomical relationships as I have suggested here and by using the bilateral weighing technique.

In Part 5 of Scientific Balance Training, we will finish looking at the Survival Totem Pole by discussing the relationships of balance to visceral function and to the pelvis and slave joints.