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Inside Spinal Pelvic Stabilizer Research
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Proprioception is defined as "sensing the motion and position of the body".1 The human body is equipped with several independent, yet interrelated mechanisms to sense and provide this necessary information. Specialized nerve endings are present in the soft tissues of the musculoskeletal system which interact with the central nervous system and coordinate our body movements, our postural alignment, and our balance. Athletic performance, in particular, relies on this delicately controlled and finely tuned system of receptors and feedback loops, and the validity of the information which is sent into the spinal cord. This coordination allows for appropriate motor responses - and sometimes, beautifully accomplished physical activities.

Proprioceptive Sensory Organ

Proprioceptive sensory organs are found in two distinct groups. Some are located in muscles and tendons, while others are within the connective tissues (ligaments and capsules) of joints (Table 1). There is a constant flow of information regarding the status and function of the musculoskeletal system from these structures to the spinal cord, the cerebellum, and the brain. When there is a breakdown in communication, or when one or more of these sensors supplies improper information, efficiency of movement decreases. Often this breakdown causes minor to severe problems with postural coordination and/or joint alignment. Sometimes it is just annoying, or it can be the source of chronic, unresolving pain.

Locations of Greatest Importance

These six specialized nerve sensors are found throughout the musculoskeletal system, in all skeletal
muscles and in every ligament, joint capsule, and articular connective tissue. Three anatomical regions, however, contain more receptors or have distinctive nerve circuits which must be considered: the foot; the spine (generally); and specifically, the upper cervical spine (Fig. 1). Because of the magnitude of sensory input, these three areas are also frequently involved in clinical
conditions. Each requires a specific approach to care.

The foot. The feet are very well supplied with proprioceptive nerve endings. Mechanoreceptors in the joints along with the muscle spindles of the foot muscles are responsible for the positive support reflexes and a variety of automatic reflexive reactions.4 These include the flexor/extensor reflex, which converts the lower limb into a firm, yet compliant pillar. Weightbearing compresses the joints and muscles, evoking reflexive activity in the extensors and inhibition of the flexor muscles.5

The spine. The paraspinal muscles have the highest concentration of muscle spindles of all muscles in the body.6 Mechanoreceptors (especially the Type IV nociceptors) innervate virtually all of the spinal and paraspinal tissues. These sensory receptors form a dense and highly sensitive network which maintains upright posture and responds rapidly to potentially damaging insults.

The upper neck. Proprioceptive organs in the upper cervical region are very sensitive to changes in postural alignment, and are a critical component (along with the vestibular system) in equilibrium and balance.7 In fact, deJong et al. were able to cause major changes in gait simply by anesthetizing the muscle and joint receptors in the neck.8

Alignment, Performance Problems

Recurrent ankle sprains. The first research to demonstrate how altered proprioceptive input predisposes to recurring alignment injuries was performed on patients with chronically sprained ankles.9 Freeman et al. called this phenomenon “articular de afferentiation” to recognize the importance of inappropriate afferent signals from injured ankle and foot proprioceptors. They pointed out that “Since articular nerve fibers lie in ligaments and capsules, and since these fibers have a lower tensile strength than collagen fibers, it seems inevitable that a traction injury to a ligament or capsule will lead to the rupture of nerve fibers as well as collagen fibers”.10

Chronic postural problems. Difficulty in achieving or keeping optimal postural alignment, or problems with excessivepostural sway, are frequently caused by inaccurate information sent by spindle sensors in chronically strained muscles or by joint mechanoreceptors.

Recurrent subluxations. When patients respond in an incomplete manner to standard chiropractic adjustments, one factor which must be considered is the status of their proprioceptive system. If inappropriate information is supplied by position receptors, the body’s movement habits, muscle tension factors, and pain patterns may remain unchanged. A 1997 study demonstrated a correlation between chronic neck pain, more frequent subluxations, and standing balance.11 This study also suggested that the involved musculature was undergoing atrophy and fatty degeneration.

Chronic pain syndromes. Another 1997 study of patients with chronic neck pain found that most had significant, unrecognized problems in the function of their proprioceptive systems.12 Many patients with chronic myofascial complaints can be shown to have inappropriate stimulation arising in the joints or muscles in the region.13

Sports performance. Performance in athletics is directly determined by the status and coordination of the proprioception system. Injury prevention, return-to-sports rehabilitation, and even winning depend to a great deal on how smoothly and quickly the musculoskeletal system can respond to position, speed, and balance changes. One of the most impressive modern approaches to improving sports performance incorporates the use of Foot Levelers’ custom-made Spinal Pelvic Stabilizer Orthotics (Fig. 2) to help improve balance and proprioceptive symmetry.14

Adjust, Support, Rehabilitate

Adjust. Many approaches to musculoskeletal problems take advantage of proprioceptive concepts. Joint adjustment, especially of the spinal joints, has a direct and immediate effect in normalizing receptor responses. This had been hypothesized for many years, based on clinical responses and neurological studies in animals.15 A 1997 study by Rogers in humans found that specific spinal manipulation was much more effective than a series of stretching exercises in improving the proprioceptive repositioning of the head in patients with chronic neck pain and positioning problems.16 A different approach was taken by Fitz-Ritson in a 1991 study which found that specific spinal manipulation effectively treated a series of patients who demonstrated cervicogenic vertigo (90% became symptom-free).17

Various soft tissue techniques, such as kinesiological and myofascial approaches, have been found to be effective in normalizing the balancing capabilities of the position receptors. Trigger point therapy (using ischemic compression, spray and stretch, or injections) seems to be able to correct imbalances in muscle tone and tension, which are perpetuated by sensory receptor problems.18

Support. Patients with proprioceptive imbalances can benefit from specific postural supports to help them achieve proper body positioning. Stude and Brink investigated proprioceptive feedback, posture, and golf performance with Foot Levelers’ SPS Orthotics.14The test subjects were experienced golfers without any specific foot or ankle problems. The researchers found that “six weeks of wearing these custom-made, flexible orthotics has a positive influence in promoting balance and proprioceptive symmetry.”

Three specific areas of improvement were identified when using the orthotics. First, there was evidence of decreased fatigue when wearing the orthotics. Next, improved symmetry was noted in the ability to balance on one leg when using orthotics. And finally, when the subjects were tested in the posture most parallel to the classic golf stance (double-leg, eyes open or eyes closed), the stabilization index was much improved with the orthotics. This demonstrated that “proprioception was significantly enhanced” by having worn their flexible, custom-made SPS Orthotics for the six-week period.

In addition to orthotic support, cervical support pillows are effective in cases of chronic neck pain, and postural back supports help to provide proper postural alignment of the back during sitting.19

Rehabilitate. Methods for postural muscle strengthening and rehabilitation have improved, based on our knowledge of proprioception. Since postural (especially back and neck) muscles are tonic, slow-twitch muscles, we must use slow and controlled exercises in an upright position, in order to stimulate and normalize input from position receptors.

In fact, closed-chain exercising is being used much more frequently in sports and rehabilitation. By keeping the body upright and weightbearing during exercising, all of the proprioceptors are recruited to condition the muscle and joints. This provides a more rapid and appropriate neuromuscular learning experience, and allows the skills practiced to be used in functional everyday and sports-specific situations (Figs. 4 and 5).

Two areas where this approach is seen are in walking and balance retraining. Walking is a basic, deeply ingrained motor pattern, sometimes called cross-crawl. Brisk walking with a good arm swing activates this neurological program, and can often help in normalizing inappropriate receptor input. Even more specialized proprioceptive exercises use gym balls,20 and balance and rocker boards.21

The Winning Formula

Greater understanding of the proprioceptive system of sensory receptors in the muscles and joints leads to improved care for many complex musculoskeletal problems. Athletes and non-athletes alike benefit when proprioception and balance are enhanced by chiropractic adjustments, custom-made SPS Orthotic support, and joint-specific rehabilitation.