The body is an interconnected chain of segments, with its base in the feet. Pedal instability can contribute to observable postural distortions, such as forward head carriage, as far up the chain as the cervical spine.
Ideal cervical spine / head posture in the standing position requires the coordination of skeletal structure, soft-tissue integrity and neurological control to resist adverse gravitational loading forces. An often-overlooked factor is the role pedal stability can play in the maintenance of proper cervical / head posture.
Faulty foot biomechanics can have a negative impact on all supporting joints above the foot-ankle complex. In particular, an unbalanced pedal foundation may, over time, contribute to a postural anterior translation (forward head carriage) in the head and neck. For maximum effectiveness, the health care professional seeking to care for a postural deviation in the cervical spine needs to evaluate the potential involvement of the pedal foundation and correct postural foot problems.
Evolution of Poor Posture
Upright posture and bipedal movement offer humans a highly functional form of ambulation, but they also promote a different variety of stressful forces on the connective tissues of the body: "the once horizontal mammalian spine wrenched upward to support the aspiring head and free the greedy hands, leaving the old vertebrate nerves and their armor crowded too closely together."1
The original biomechanical human profile, directed by survival, was primarily a dynamic one, "built for mobility rather than stability."2 Yet over time, human beings have assumed a less consistent, less dynamically optimum biomechanical physical stature on a daily basis. "Compared to primitive man living an outdoor life, civilized man has become a standing-around and a sitting-down animal rather than a running-around one."3
A 2012 well-publicized study by the National Health and Nutrition Examination Surveys revealed 50-70 percent of people spend six or more hours each day sitting.4
A sedentary lifestyle and/or compromising posture places strain on the ligaments, tendons, muscle fibers, fasciae, cartilage and bone in an attempt to maintain equilibrium of the body. (Is it any wonder recent studies have linked the "sitting disease" to increased risk of a number of cancers, obesity, diabetes and premature death?)5 "Many painful, disabling conditions of the soft tissues of the musculoskeletal system are directly or indirectly related to posture in standing, walking, moving, lying, sitting, bending, or lifting."6
Up to one-third of workers in the United States are required to perform manual activities on a daily basis that are damaging to the musculoskeletal system.7 These potentially harmful tasks often involve stationary, imbalanced postures and dynamically uncoordinated movements.
In dealing with neuromusculoskeletal health maintenance, it is basic and imperative that health care specialists take into account and include in their exams an evaluation of an individual's habitual posture and its potential role in pain and disability. If postural faults were only of aesthetic consequence, the concern about them might be limited to appearance. But this is not the case, in that postural abnormalities may cause discomfort, pain or deformity.6,8-9
The Biostatic Chain
During walking and running, the spine is one link in a biomechanical kinetic chain in which movement at one joint influences movement at other joints in the chain.10 This concept of a chain also applies to the body in a motionless, standing posture; however, the terms biomechanical static chain or biostatic chain is more appropriate, since directed movement is not involved. In either case, the chain extends from the feet through the ankle, tibia, knee, femur, hip joint, pelvis and spine – right up to the head.
The integrity and effectiveness of this chain depend upon a fine balance of body alignment and muscle-restraining activity at each joint against gravitational pull downward. Passive stability is achieved when the center of gravity of each segment is aligned directly over the center of the supporting joint. When the body is erect and weight evenly distributed between the feet, there are minimal demands for muscle action because there is no forward motion.
While in theory, stability of the biostatic chain should be realized without any muscle action at all, the fact not one of the supporting joints (pelvis downward through feet) is locked means the slightest sway (the beating of the heart, for example) can create an unstable alignment.4 Therefore, postural balance means a continuous involvement of the supporting skeletal structure and muscles.
Chain Reaction of Distortions
In ideal standing posture, the feet evert to form an angle of 30 degrees, and a plumb line dropped from the sacral promontory falls midway between the feet onto a line between the navicular bones.11 Pronation occurs when the superior aspect of the calcaneus tilts and rolls inward, bringing the talus with it. This releases the navicular from arthrodial articulation with the talus and jeopardizes the medial longitudinal arch. When collapsed, it can begin serial distortion that may extend to the occiput.
Because pronation involves the talus, it can draw the adjacent tibia into rotation. The movement extends further to the femur, bringing the greater trochanter forward and out. The piriformis muscle at the apex of the trochanter is then subjected to a windlass-type stretch. Due to its connection with second, third and fourth sacral segments, the sacrum at its articulation with the ilium on the involved side may be pulled into a subluxated anterior and inferior position.
When this occurs, the gluteus maximus muscle compensates by contracting to resist the downward and forward disposition of the pelvis. At its origin on the posterior third of the iliac crest, the gluteus maximus contraction may force the ilia portion of the innominate to rotate posteriorly. Thus begins a typical basic distortion.
Likewise, with the sacrum in an anterior and inferior position, the fifth lumbar vertebra is mobile. Following Lovett's Law, it will rotate toward the side and introduce structural scoliosis.
According to Free, the trapezius muscle "may tighten on the same side as the hypertonic hamstring, creating an inferior occiput and an atlas laterality. Subluxations may occur at the atlanto-occipital or the atlanto-axial area, with cervical pain on the side of the tight hamstring. If this cervical compensation occurs, the patient will have pain on the entire side (cervical, thoracic, lumbar) and many times the leg and arm."12
Porterfield writes that "the cervical spine may be only one component of neck pain complaints. Structures related to the upper extremity and head often are involved with the painful syndrome, and an examination of these structures reveals alteration in function."13
Editor's Note: Dr. Charrette discusses evaluation and conservative care options in part 2 of this article.
References
- Sims M. Adam's Navel: A Natural and Cultural History of the Human Form. New York: Viking, 2003.
- Perry J. Gait Analysis: Normal and Pathological Function. Thorofare, NJ: SLACK, Inc., 1992.
- Zacharkow D. Posture: Sitting, Standing, Chair Design and Exercise. Springfield, IL: Charles C. Thomas, 1988.
- Owen N, et al. Sedentary behavior: emerging evidence for a new health risk. Mayo Clin Proc, 2010;85(12):1138-41.
- Biswas A, et al. Sedentary time and its association with risk for disease incidence, mortality, and hospitalization in adults: a systematic review and meta-analysis. Ann Intern Med, 2015;162(2):123-132.
- Cailliet R. Soft Tissue Pain and Disability, 3rd Edition. Philadelphia: F.A. Davis, 1996.
- Chaffin DB. The Value of Biomechanical Assessments of Problems of Load Handling, Workplace Layouts, and Task Demands. In: Hayes KC, et al. (eds.) Biomechanics IX-B. Champaign, IL: Human Kinetics Pub., 1983.
- Kendall HO, et al. Posture and Pain. Malabar, FL: Robert E. Krieger Pub. Co., Inc., 1992.
- Travell JG, Simons DG. Myofascial Pain and Dysfunction: The Trigger Point Manual, Volume 2. Baltimore: Williams and Wilkins, 1992.
- Steindler A. Kinesiology of the Human Body Under Normal and Pathological Conditions, 3rd Edition. Springfield, IL: Charles C. Thomas, 1970.
- Cailliet R. Foot and Ankle Pain, 2nd Edition. Philadelphia: F.A. Davis, 1983.
- Free RV. Some common denominators in spinal misalignments, part 2. Digest Chiro Econ, 1988;30(6):128-129.
- Porterfield JA, DeRosa C. Mechanical Neck Pain: Perspectives in Functional Anatomy. Philadelphia: W.B. Saunders Co., 1995.
Click here for previous articles by Mark Charrette, DC.