The Pettibon Weighting SystemTM

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 consists of specially designed head, shoulder and hip weights that patients wear. 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's 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.

Why Isometric Exercises?

Two kinds of muscle fibers make up the musculoskeletal system. One is fast-twitch muscle fiber. The other is slow-twitch muscle fiber. Muscles 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 muscles. 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 aligned.

Isometric exercises, which involve pushing against a force that moves very slowly or doesn’t move at all, help eliminate postural muscle spasms as well as rehabilitate 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

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 happens whether 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 like CBP. 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.


Deformation: 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

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.


Plasticity: 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.


Creep: 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.


Hysteresis: 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 repositioned before the holding energy is regained. Within 15 to 20 minutes of inactivity, the holding energy is regained.

Specific Pettibon equipment produces hysteresis. You'll be introduced to those in the next section, where we go over The Pettibon System's key components. Threaded through the explanations will be how soft tissue physiology and function are applied.