Chiropractic Biophysics

Chiropractic BioPhysics, known as CBP, defines a correct spine as a geometric shape and treats every measured departure from it as the disorder. Donald D. Harrison named the method in December 1980 for physics applied to biology in chiropractic. A CBP examination records standing posture as rotations and translations of three body masses, then measures the sagittal curves on standing films against a published model. Treatment loads the body in the exact opposite direction of every displacement found, using adjustments, exercises, and traction held for 10 to 20 minutes.

Chiropractic BioPhysics began when Donald Harrison stopped teaching another man’s technique

Harrison spent the late 1970s as the principal instructor of the Pettibon technique. Dissatisfied that it did not reliably produce lasting correction, he began substituting his own methods in selected cases. Deed Harrison and Paul Oakley date the decisive case to about 1980, and describe it as the point at which Harrison concluded the body had to be treated mathematically. He coined the term mirror image adjusting to name what followed. The technique itself was named that December by Donald Harrison, Deanne Harrison, and Daniel Murphy.

The training behind that decision was unusual for a chiropractor and explains what the method became. Harrison took a bachelor’s degree in mathematics from the University of Washington in 1968 and a master’s in mathematics from the University of Texas at El Paso in 1971. He earned his Doctor of Chiropractic from Western States Chiropractic College in 1979, then returned to graduate engineering. The University of Alabama in Huntsville awarded him a master’s in mechanical engineering in 1997 and a PhD in applied mathematics in 1998.

The mathematical foundation came from outside chiropractic. In 1974 Manohar Panjabi, Augustus White, and Richard Brand published a short note in the Journal of Biomechanics proposing a Cartesian coordinate system for describing the configuration of body parts (Panjabi 1974). Harrison was the first to apply that system to upright human posture. He published the full treatment as a linear algebra approach to posture in the Journal of Manipulative and Physiological Therapeutics in 1996 (Harrison 1996). He founded the CBP research foundation with Deanne Harrison in 1982 and co-founded the American Journal of Clinical Chiropractic in 1991. The International Chiropractors Association named him Chiropractor of the Year in 2006. He died on July 20, 2011, at 65.

The Harrison spinal model states what a normal spine should look like, in degrees and ratios

CBP’s first premise is that a normal static spinal configuration exists and can be written down. The Harrison model does not describe the bones. It describes one continuous path across all three regions, the posterior longitudinal ligament, traced along the backs of the vertebral bodies from C2 to the top of the sacrum. That path was chosen because it is the line a clinician marks on a lateral radiograph.

The cervical lordosis is modeled as an arc of a circle

The founding modeling study appeared in Spine in March 1996 and analyzed 400 subjects (Harrison 1996). Films showing any segmental or total kyphosis were excluded, as were moderate to severe degenerative changes, because the object was a model of a lordotic neck. Of the 400, 252 were asymptomatic. Hand measurements were compared against a Fortran model that took each subject’s height over length ratio and returned predicted segmental angles.

The numbers the model returns are the specification. At an 86.73 percent height over length ratio it predicts an atlas plane line of 23 degrees and a total C2 to C7 angle of 34 degrees. Below that it predicts 7.5 degrees from C2 to C3 and 6.6 degrees at every remaining segment. The curve is a uniform arc. The second cervical vertebra is treated as roughly 40 percent larger than its neighbors, because no disc sits above it. A follow-up study in Spine in 2004 ran circular and elliptical modeling across 72 asymptomatic subjects, 52 acute neck pain subjects, and 70 chronic neck pain subjects (Harrison 2004).

The thoracic and lumbar curves are portions of ellipses

Thoracic modeling in Journal of Spinal Disorders in 2002 tested circular and elliptical shapes against 80 asymptomatic subjects (Harrison 2002). The lumbar work reached the Journal of Orthopaedic Research in 1998, led by Harrison’s doctoral advisor Tadeusz Janik and built on 50 normal subjects (Janik 1998). Fitting the lumbar data required original mathematics, an inverse of an infinite series of elliptical tangent lines.

The result is one continuous model in three parts, each an ellipse with its own minor to major axis ratio. The thoracic curve carries greater curvature toward the head and straightens at the thoracolumbar junction. The lumbar curve carries greater curvature toward its base. The cervical curve is the special case in which the two axes are equal, which is what makes it circular. CBP states its treatment goals against this model as absolute rotation angles near 35 degrees from C2 to C7 and 40 degrees from L1 to L5.

Ideal posture is defined as the absence of twelve displacements

Posture is analyzed separately from the curves, in the same coordinate language. The head, the rib cage, and the pelvis are treated as rigid bodies, each described relative to the mass below it. The head is read against the thorax, the thorax against the pelvis, and the pelvis against the feet. Each body mass has six degrees of freedom, three rotations and three translations, which gives twelve possible displacement directions. Harrison named each opposing pair a mirror image. Ideal posture is the condition in which none of these displacements is present, so that the centers of mass of skull, thorax, and pelvis stack vertically in both the front and side views.

Working through that grid, Harrison found that half of all human postural movements had no published data. Forward head posture was the one that did. His group went on to publish normal ranges for the unstudied ones, including lateral head translation and anterior and posterior thoracic translation. A pure lateral translation of the thorax produces a curved-looking spine with little or no vertebral rotation, which CBP calls pseudoscoliosis and treats as a different object from true scoliosis.

Mirror image adjusting is CBP’s signature idea, and it runs on subtraction

Harrison originated the mirror image setups in March 1980, and the logic is a direct consequence of describing posture as vectors. If a displacement is a translation of so many millimeters along one axis, the correction is the same translation with its sign reversed. The patient is physically placed in that reversed position before any force is applied. In the front view the head, rib cage, or pelvis is reflected across the median sagittal plane. In the side view it is repositioned across the mid frontal plane.

The dosing rule goes further than simple reversal. Soft tissue needs substantial stress and strain before it will hold a new resting length. Harrison therefore specified a setup applying “twice the negative of the translation distances and rotation angles” found on examination. Overcorrection is the design. Donald Harrison and his brother Glenn Harrison built the delivery methods for each of the twelve positions, using drop tables and both table-mounted and hand-held instruments. CBP’s own account of the mechanism is neurological rather than purely mechanical: the setups are performed to reset the nervous system’s regulation of postural muscle balance.

Exercise applies the same reversal under the patient’s own muscle

Between 1980 and 1986 Donald and Glenn Harrison developed mirror image exercises on the identical principle. The patient actively drives the body mass into the opposite of its measured position, using body weight alone or an elastic band for added resistance. The stated purpose is to stretch what has shortened and strengthen what has weakened around an asymmetric posture. Exercise, adjustment, and traction together form what CBP calls the E.A.T. protocol, and the three are prescribed from the same measurement set.

CBP treats sustained traction as a primary intervention rather than an adjunct

CBP holds a corrective load for 10 to 20 minutes per session, on the reasoning that viscoelastic deformation of the resting length of ligaments, muscles, and discs requires sustained loading rather than an impulse. Every other named technique in this library delivers force in milliseconds. Traction is the prescription aimed at the curve, and the adjustment and the exercise are arranged around it.

The film selects the traction setup

The setups are specific and are matched to the measured pattern rather than to the complaint. Hypolordosis with mild anterior head translation is assigned compression extension traction. Slight kyphosis with posterior head translation is assigned two-way non-compression traction. Reversal of the upper cervical curve with mild anterior head translation is assigned compression extension two-way traction. Lumbar kyphosis with anterior thoracic translation is assigned three-point bending extension traction, standing or supine. Thoracic hyperkyphosis is assigned three-point bending thoracic traction.

The hardware has its own lineage. The first cervical extension traction used an inclined bench with a camlock and pulley system pulling on the forehead. Dwight DeGeorge of Saugus, Massachusetts developed it with Tony Gambale. Pope’s two-way traction added a posterior to anterior pull through the mid cervical spine while the seated head is extended and distracted. A chin and forehead strap converts that into extension compression two-way traction. The Denneroll cervical orthotic is the low-technology version, and Deed Harrison developed the precision vectors for lumbar extension traction in the mid 1990s.

Traction is screened for, then ramped

Extension compression traction is not applied to everyone. CBP screens out disc herniation, stenosis, and radiculopathy before loading a neck into hyperextension. That screen is one of the method’s stated reasons for taking films first. Loading is then built up gradually. In the 2021 Scientific Reports trial the Denneroll sessions began at 3 minutes and rose by 1 to 2 minutes per session until they reached 20 (Moustafa 2021). Structural rehabilitation is then prescribed in blocks, either 3 times a week for 12 weeks or 4 times a week for 9 weeks, both reaching 36 sessions. An initial 6 to 12 visits of relief care usually precede the block.

CBP reads the radiograph with tangent lines and turns the measurement into the prescription

The Harrison posterior tangent method draws lines flush with the posterior margins of the vertebral bodies. The angle between the top and bottom tangents of a region is the absolute rotation angle, and the angle between two adjacent tangents is a relative rotation angle. The segmental angles must sum to the regional angle, which gives the clinician an arithmetic check on the marking. Global curves are usually taken as C2 to C7, T1 to T12, and L1 to L5, and translation distances are read as the horizontal offset between named vertebrae.

The choice of the posterior margin is deliberate. Those margins are less distorted by osteoarthritic change than the anterior ones, and a tangent to the curve is its first derivative, so the intersection of two tangents describes the local configuration directly. A 2000 Spine comparison put the standard error of measurement for the tangent method near 2 degrees against 4.5 to 10 degrees for the Cobb method (Harrison 2000). Reliability of the full line drawing set, including the modified Risser-Ferguson method used on front views, was reported in 2002 (Harrison 2002). On the front view the normal cervicothoracic upper angle is 90 degrees and both the lower angle and the Rz angle are 0.

Positioning is part of the measurement

CBP standardizes the stance, because posture measured in another stance is another number. Films are taken standing, without shoes, heels at hip width. The patient closes the eyes, nods the head a few times, stops where it feels natural, then opens the eyes. Nothing about the posture found is corrected before the exposure. Whatever the patient is doing is the data.

Identical postures conceal different spines, which is why CBP films rather than eyeballs the posture. Three lateral cervical radiographs can each show about 25 millimeters of forward head translation and still differ completely underneath, one hyperlordotic, one hypolordotic, one kyphotic. CBP calls these harmonics, and each one carries a different protocol. A hyperlordotic neck is never given extension exercises, and a fully kyphotic neck is never given head retractions.

The CBP research program is the largest measurement effort attached to any single chiropractic technique

CBP NonProfit, Inc. runs out of Eagle, Idaho as a 501(c)(3) corporation, founded in 1982 and incorporated under that name in 1989. It lists more than 300 peer-reviewed spine and chiropractic publications and a board of 13 doctors. Seven CBP textbooks carry the protocols. Deed Harrison lists roughly 234 peer-reviewed spine publications of his own and has guest edited two Journal of Clinical Medicine special issues on spine rehabilitation.

The output falls into recognizable design families. Geometric modeling studies cover each spinal region. Reliability studies cover the line drawing and positioning procedures. Biomechanical loading studies use elliptical shell and postural loading models. On top of those sit non-randomized controlled trials, randomized controlled trials, and well over 100 case reports and series. The first controlled trial appeared in the Journal of Manipulative and Physiological Therapeutics in 1994 (Harrison 1994). It ran three arms at 5 sessions a week for 10 to 14 weeks: one untreated, one adjusted, and one adjusted plus extension compression traction. Deed Harrison and Paul Oakley’s 2022 book chapter is the method’s current overview (Harrison and Oakley 2022).

Where Chiropractic Biophysics meets the Unified Model of Tone

CBP is the most structurally committed technique in this library, and the Unified Model of Tone is not a structural model. The disagreement is worth stating in full, and it resolves into one point. Twenty minutes under load is a different kind of input from a thrust.

Harrison held that one ideal alignment exists and that departure from it is the disorder

Three premises carry it. A normal and ideal static spinal configuration exists. Abnormal alteration of the spine and posture produces abnormal function and disrupts homeostatic balance. Altered static alignment produces altered dynamics. Harrison put numbers on all three, down to 6.6 degrees per cervical segment and a 2 degree measurement error. Nothing in CBP is hedged about this. The geometry is the diagnosis, the geometry is the goal of care, and a follow-up film is how the method judges itself.

We hold that tone is the organization, and that shape is one of its projections

Tone is the integrated organization through which the body’s many processes relate to one another at a given moment. It spans mechanical tension, neural excitability, autonomic regulation, sensory gain, and prediction. Shape is one reading of that state rather than the state itself. A lateral film resolves vertebral position to a tenth of a millimeter and reports nothing about excitability, autonomic outflow, or sensory gain at the same level. Two people can share a curve to the degree and hold that curve in entirely different tension states.

Geometry and tension are the same variable read two ways

Both positions hold at once. The body is a prestressed tension network in which bones float rather than stack, an architecture Stephen Levin set out for the spine in 2002. The model adds a claim to that architecture. The integrated tensional state of the network is how the body knows its own shape. Geometry is the current organization of the tissue rather than a picture kept somewhere else.

That makes a sustained change in curve a sustained change in load, and a sustained change in load a change in what every mechanoreceptor in the region reports. CBP arrived at the same coupling from the engineering side and named it. A rotation or translation of a body mass is the main motion. The segmental displacements that accommodate it are the coupled motions. Harrison was measuring the mechanical face of one variable. The model’s addition is that the tension he was loading is also the body’s account of where it is.

Traction held for 20 minutes is a different doorway from every thrust technique here

Time course is a foundational part of tone, and CBP is the one technique in these 33 that makes it the primary variable. A thrust is an impulse. It delivers a large amount of information in a few milliseconds and asks the nervous system to sort out what happened. A 20 minute hold delivers very little information per instant. It holds the resting condition the system regulates around, long enough for the tissue’s report to follow the load. Across 30 to 40 sessions the input stays a sustained condition rather than a series of questions.

This is why the model does not need CBP’s exclusivity claim to be true to explain what CBP does. There is no single lynchpin and no single correct dose. An input can reach the whole organization from more than one place and at more than one speed. The Gonstead thrust, the Atlas Orthogonal stylus, and a Denneroll under a neck for 20 minutes are all genuine doorways at once.

What the model predicts about Chiropractic BioPhysics

The first is a covariance prediction. If curve geometry and neural state are readings of one variable, they should move together within the same person over the same weeks. The design already exists. The 2021 Scientific Reports trial randomized 80 subjects aged 18 to 25 into a Denneroll arm and a placebo towel arm. Each ran 30 sessions over 10 weeks. Alongside cervical lordosis and anterior head translation the trial recorded somatosensory conduction time and the amplitudes of the spinal N13, brainstem P14, parietal N20 and P27, and frontal N30 potentials. The model predicts that the geometric and the neural measures share one organization subject by subject, with compensation deciding how closely the two run at any visit. Measures that varied independently would falsify the unification claim, with no reinterpretation available.

The second is a bidirectional prediction. CBP already prescribes opposite loading for hyperlordosis and hypolordosis, which makes it one of the few methods with both directions built into its protocol. The model predicts that a matched input moves patients displaced in both directions toward the same middle and narrows the spread of the group, against a sham matched for contact time and attention. A uniform shift in one direction, moving everyone the same way regardless of where they started, would refute it. Both of these are the model’s predictions rather than CBP’s findings.

Who carries Chiropractic BioPhysics forward

Deed E. Harrison, DC, leads the method. He graduated from Life Chiropractic College West in 1996, practiced in Elko, Nevada from 1997 to 2011, and is President and CEO of CBP Technique and Seminars as well as President of CBP NonProfit. He chaired the PCCRP chiropractic radiography guidelines and reviews manuscripts for Spine and the European Spine Journal. Paul A. Oakley is the method’s most active co-author. Joseph Ferrantelli built the PostureRay radiographic digitization software the protocol prefers.

Training runs through seminars rather than a college curriculum. General certification requires 7 seminars totaling roughly 90 hours. They cover radiographic and postural protocols, mirror image adjusting, upper cervical analysis, and structural rehabilitation of all three spinal regions. The examination is 45 multiple choice questions plus a marked line drawing and mock adjustments. Advanced certification adds 7 further courses for roughly 180 hours combined, examined by presenting a patient case at the annual conference. Both levels require one CBP seminar every 2 years. Teaching runs out of the CBP Doctor Institute in Eagle, Idaho, an 11,000 square foot facility with a 2,000 square foot conference center.

How this page relates to the rest of the library

Gonstead is the other radiographically driven method in these 33, and the contrast is in what the film is allowed to decide. Gonstead makes the film one of five criteria and gives it a job it may not exceed. CBP lets the measurement generate the prescription outright, down to which traction unit the patient is placed in.

Atlas Orthogonal is the other method that converts a marked angle into a prescribed correction, and it sits at the opposite end of every physical axis. One bone against the full spine, and ounces against pounds, from the same starting move of drawing lines on a film.

Diversified is the contrast on force. It is the high velocity low amplitude thrust most of the profession trains in. CBP borrows it for the first 6 to 12 relief visits.

Orthopedics covers the joint mechanics CBP’s modeling studies operate on: disc loading, vertebral body stress, and connective tissue behavior under sustained load.

The Unified Model of Tone sets out the tension network architecture and the foundational dimensions of tone that the section above applies, including the treatment of time course as a variable in its own right.