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How the Pettibon System Works

The Most Advanced System For Spinal and Postural Correction

“The nervous system controls all other systems and relates the individual to his or her environment.” —Gray’s Anatomy, 29th American Edition, Page 4

Humans develop, act and react in time and need to their environment under the direction and control of the nervous system. For Pettibon practitioners, humans’ functional spinal environment is gravity. And gravity is an absolute environment to which the upright spine and posture must develop and relate to.

The role that gravity plays in how abnormal spinal form develops is fundamental to Pettibon chiropractic principles. As Dr. Pettibon explains, “The nervous system always wants us to hold our heads upright. And the nervous system will do this at the expense of displacing the lower spine.”

Key Principles

The Pettibon Spinal Model™

The Pettibon Spinal Model at Naperville Inst.

Opposing Lever-Arm Units

  • Gravity is an absolute environment to which the upright spine and posture of humans must develop and relate.
  • Since gravity is an absolute, there has to be an absolute optimal position for the upright spine and posture.
  • The skull is a vertebra. It’s the only vertebra that knows its neurologically optimal position and has the ability to establish and maintain that posture.
  • The normal spine is composed of six opposing lever-arm units. The units’ division is based upon muscle attachment and function.
  • The global spine’s position relative to gravity is more important than its units or its segments.
  • Individual spinal vertebrae, with the exception of the skull-atlas, do not move out of normal position independent of their unit and become displaced without soft tissue compromise.
  • Posture is controlled neurologically. Righting reflexes and the cerebellum regulate the skull’s upright position—keeping the skull upright even at the expense of displacing the lower spine.
  • A less than optimum lateral and A-P spine and posture compromises spinal function.

The Pettibon Weighting System™

The Pettibon Weighting System at Naperville Inst.How then do Pettibon practitioners take these principles and put them into practice by re-aligning the spine so that it can function optimally in its upright position relative to gravity? They apply the science at the core of The Pettibon System: The patented Pettibon Weighting System.

The Pettibon Weighting System posture correction tool consists of specially designed head, shoulder and hip weights that patients wear for up to 20 minutes daily until the spine is corrected. The amount of weights and their placement depend upon the spinal displacement that needs to be corrected.

How the weights work: Wearing the weights alters the head’s, thoracic cage’s and pelvis’ centers of mass, causing the righting reflexes to send spine correcting sensory input to the nervous system. To balance the body to the weights, the nervous system’s innate organizing energy causes some involved spinal muscles to relax and others to contract, thereby repositioning and correcting the spine and posture relative to gravity. Additionally, the weights make the involved muscles do isometric exercises, needed to restore their strength, endurance and balance to reach posture correction.

Why Isometric Exercises?

Two kinds of muscle fibers make up each muscle bundle of the musculoskeletal system. One is fast-twitch phasic muscle fiber. The other is slow-twitch postural muscle fiber. Muscle bundles have both types of fibers but usually one fiber type dominates a muscle group. Our postural muscles have mostly slow-twitch fiber.

In the gym, when we’re ‘pumping iron’ and doing aerobic exercises, we’re affecting fast-twitch muscle fiber or phasic fibers. What’s happening to our postural muscles? Not much. So exercises to strengthen phasic muscles don’t improve posture.

When phasic muscles fatigue and/or when they’re injured they go flaccid and collapse. Postural muscles react very differently from phasic muscles when they’re injured or fatigued: they spasm. And the way postural muscles spasm is rarely even, either side-to-side or front-to-back. That’s why poor posture distorts our appearance because our spine is no longer in a normal position. Isometric exercises, which involve pushing or pulling against a force that moves very slowly or doesn’t move at all, help eliminate postural muscle spasms as well as rehabilitate and correct their balance, strength, and endurance.

Soft Tissue Physiology & Function

There is, of course, much more to The Pettibon System. But before taking a closer look at a few key individual components and how they’re organized into a comprehensive system, let’s go over some physiological properties and function of soft tissues. Why?

For Pettibon practitioners, the spine is viewed as a closed kinetic system made up of hard and soft tissues. The soft tissues—muscles, discs, and ligaments—hold the spine upright in its optimum position for function relative to gravity, while moving it through its expected ranges of motions. So spinal correction has to involve the entire spine rather than just one segment or vertebrae. An example: If ligaments are torn in the lumbar spine, the part that’s torn allows aberrant motions which often cause pain and dysfunction in other areas of the spine such as the neck. The neck pain and dysfunction won’t be resolved until the torn ligament and aberrant motion are treated first.

Three different types of forces can injure the spinal system: sudden applied, repetitive, and cumulative. A whiplash is the most common example of a sudden applied force. Repetitive and cumulative forces come from time dependent functions of our positions over long periods. In other words, the spine’s positions in work, play, or daily living activities like sleeping, reading, watching TV, etc. Understanding how soft tissues react to these forces provides the reasons why conventional chiropractic doesn’t produce permanent spine and posture correction. And more importantly, it explains why The Pettibon System does!

Dynamic Stretch Reflex & Static Stretch Reflex

Dynamic Stretch Reflex & Static Stretch Reflex at Naperville Inst.When a muscle—especially a muscle that hasn’t been warmed up—is suddenly stretched, an instant dynamic stretch reflex causes muscle contraction. Our body is protecting the position of its parts from changing. The dynamic stretch reflex happenswhether the sudden stretch was intentional—from an adjusting thrust—or accidental.

The static stretch reflex always immediately follows the dynamic stretch reflex. This reflex continues muscle contractions that oppose the stretched muscle. These contractions last for hours but not days.

Now consider conventional chiropractic adjustments and some techniques. They’re high velocity, low amplitude thrusts delivered into the spine to induce joint movement. So after a conventional chiropractic adjustment, the dynamic stretch reflex causes the muscles to reposition the changed spine back to its original displaced position. Then the static stretch reflex continues muscles contractions that oppose the stretch. This is why it’s possible for the spine’s position to become more displaced than before it received a ‘so-called’ adjustment.

Let’s go over how stretched muscles react. Their physiological properties and function are: deformation, visco-elastic stretch, plasticity, creep, and hysteresis.


The change in the form of a structure. We consider all changes in the spine’s form to be a deformation. And we categorize deformations as ‘bad’ or ‘good’. A ‘displacement deformation’ is bad because it deforms the spine away from its normal, optimal functional position. ‘Correction deformation’ is good because it moves the spine back or toward its optimal functioning position.

Visco-elastic Stretch

Spring-like deformation. The fibers in spinal ligaments and discs have this property. Ligaments’ visco-elastic stretch along with muscle reflexes are what cause vertebrae to deform back to their displaced position after the force of an adjusting thrust is removed.


The property of a material to permanently deform when it’s loaded beyond its elastic range. Consider an intact spring. If you load it—stretch it—beyond its elastic range, it becomes permanently elongated. Subject a ligament to greater than 40% of its ultimate load, and it also can be permanently elongated. That’s how ligaments are torn. Accidents involving whiplash typically result in ligament tearing.


Wobble Chair Warm Ups & Exercises | Naperville Inst.



How a visco-elastic material deforms (changes) into the shape it’s held in when it’s subjected to a constant, applied load over time. You just learned that the spine’s ligaments and discs are visco-elastic material. Because of their spring-like ability, a force applied for a short period of time won’t change their positions. They’ll ‘spring back’. But subjecting the spine’s ligaments and discs to a constant, applied load deforms (changes) them into the shape they’re held in over time.

An example of creep is how an individual’s height, after standing or sitting all day, can be less at night than in the morning. The individual is shorter at night because the compression forces the nutrition-filled fluids out of the inter-vertebral discs and ligaments. Similarly, people’s position over long periods of work, play, or their daily living activities such as the position they sleep in, watch television, read, etc. can cause discs and ligaments to creep.

Creep deformation of the discs and ligaments must be arrested and reversed daily. If it isn’t, the fallout is dysfunction, spinal joint pathologies, nerve compression, and chronic pain. These same conditions are also considered the natural consequences of the aging process. The prevailing belief is that nothing can be done to correct these problems. Not true! Soft tissue creep can be arrested and reversed daily if hysteresis is produced in the ligaments, discs, and tendons.


A phenomenon associated with energy loss exhibited by viso-elastic materials when they’re subjected to progressive loading and unloading cycles over time.

Ligaments, discs, and tendons, have holding energy. Loading and unloading cycles through compression and traction cause the temporary loss of this energy or hysteresis. Hysteresis changes the nucleus pulposis of the discs from hydro-gel, a Jell-O like resistance to motion, into hydro-sol, water-like solutions with limited resistance to positional changes. When the soft tissue’s resistance is significantly reduced, then the joints can easily be re-positioned before the holding energy is regained. Within 15 to 20 minutes of inactivity, the holding energy is regained.

Specific Pettibon equipment produces hysteresis.