THE EFFECT OF LOW FORCE CHIROPRACTIC

ADJUSTMENTS FOR 4 WEEKS ON BODY SURFACE

ELECTROMAGNETIC FIELD

John Zhang, MD, PhD,a and Brian J. Snyder, DCb

ABSTRACT

a Associate DireCollege of Chirop

b Research Proffield, Mo 63017.Sources of fundSubmit requests

Department, LoganChesterfield, MOPaper submitted

2003.

0161-4754/$30.Copyright D 20doi:10.1016/j.jm

Objective: To study the effects of 4 weeks of low-force chiropractic adjustments on body surface electromagnetic

fields (EMFs).

Method: Thirty-five chiropractic students randomly assigned into control (17 subjects) and experimental groups (28

subjects). A triaxial fluxgate magnetometer was used for EMF detection. The subjects’ body surface EMF was determined

in the prone position before and after the chiropractic adjustment. A Toftness low-force chiropractic adjustment was

applied to the cervical, thoracic, lumbar, and sacral areas as determined by the practitioner. Heart rate variability analysis

was recorded once a week to determine autonomic nervous system activity in both the control and experimental groups.

Results: The EMF on the subjects’ body surface decreased after chiropractic adjustment at the cervical, thoracic, lumbar,

and sacral regions in all 6 visits during the 4-week treatment period. The EMF showed a downtrend over the 4-week period

after the low-force adjustment. The same changes were not observed in the control group. The chiropractic adjustment

group had a slight decrease in heart rate over the 4-week treatment period, and no significant change was observed in the

control group. Heart rate variability analysis did not show consistent changes before and after the low-force adjustments

during the treatment period.

Conclusion: Low-force chiropractic adjustment in the cervical and thoracic areas resulted in a consistent reduction of

the body surface EMF after 4 weeks of active treatment. No statistically significant differences were found in the heart rate

and heart rate variability in the 4-week study. (J Manipulative Physiol Ther 2005;28:159-163)

Key Indexing Terms: Manipulation; Chiropractic; Electromagnetic Field

Exposure to natural or man-made electromagnetic

fields (EMFs) may be linked to health hazards such

as cancer, abnormal behavior, memory loss, Parkin-

son’s disease, Alzheimer’s disease, sudden infant death

syndrome, suicide, and psychosomatic effects.1 Electro-

magnetic field is associated with the presence of electric

charge or potential (electric fields are measured in Newtons/

Coulombs) and electric current (magnetic fields are meas-

ured in Tesla).2

ctor of Research, Research Department, Loganractic, Chesterfield, Mo 63017.essor, Logan College of Chiropractic, Chester-

ing: none declared.for reprints to: John Zhang, MD, PhD, ResearchCollege of Chiropractic, 1851 Schoettler Road,

63017 (e-mail: John.Zhang@Logan.edu).June 17, 2003; in revised form September 23,

0005 by National University of Health Sciences.pt.2005.02.009

There are extensive studies on the biological effect of

EMF on animal and human bodies. Gmitrov et al3 reported

that in conscious rabbits, local application of 0.35 T to

sinocarotid baroreceptors increased blood pressure, heart

rate variability (HRV), and microcirculation.3 Electromag-

netic field exposure in healthy volunteers resulted in

significant increases in time domain and spectral analysis

of HRV.4 It is noticed that most reports are on the harmful

effects of the high environmental EMF in animals and

humans,5,6 and very few studies focus on the beneficial

effect of lower EMF in humans.

One theory proposed by Toftness is that a chiropractic

adjustment on specific body surface areas could change the

body surface EMF.7-10 Based on Toftness’ theory, clinical

studies using Toftness adjustments have shown that specific

chiropractic adjustment reduced symptoms in acute and

chronic back pain, basilar migraine, chronic tension head-

aches, and primary dysmenorrhea.11-18 Despite the claim

that Toftness chiropractic adjustment may reduce body

surface EMF, using a quantitative instrument to study EMF

changes before and after low-force Toftness chiropractic

adjustment has not been reported. The purpose of this

intermediate-term 4-week controlled study was to inves-

159

Fig 1. Cervical EMF changes before and after Toftness adjustments.

Fig 3. Thoracic EMF changes before and after Toftness adjust-ments.

Fig 5. Lumbar EMF changes before and after Toftness adjustments.

Fig 7. Sacral EMF changes before and after Toftness adjustments.

160 Journal of Manipulative and Physiological TherapeuticsZhang and Snyder

March/April 2005Surface Electromagnetic Field

tigate the changes in EMF on human body surface before

and after a low-force Toftness chiropractic adjustment.

METHODS

A total of 35 students from a college setting were

recruited and randomly assigned into the control (17

subjects) and experimental groups (28 subjects) using a

random table. Subjects in the control group received no

chiropractic adjustment. The participants had not been

exposed to the low-force chiropractic adjustment at least

3 weeks before this study. Any individuals with cardiac

infarction, heart failure, osteoporosis, or bone pathology

were excluded from the study. Individuals who did not

comply with the written informed consent form were

excluded from the study. The Logan College of Chiropractic

institutional review board approved this study.

A nonmotorized adjusting table was used for all tests

with the subject resting comfortably in a prone position.

A motorized adjusting table was tested for EMF strength

for comparison with the nonmotorized adjusting table.

The practitioner delivered a low-force (2-32 oz) Toftness

chiropractic adjustment by a metered handheld pressure

applicator at the cervical, thoracic, lumbar, and sacral

contact site.16,18 This applicator is a rubber-tipped, spring-

loaded device that indicates the amount of force that is

being applied at the contact site. The adjustment contact line

of drive, amount of force applied, and duration of the

contact are determined by constant monitoring of the

adjustment site with the sensometer which consists of an

open cone and a Mylar membrane.16 The specific adjust-

ments for the various levels of the spine were documented

and recorded on each of the subjects. The parameters

included the amount of time and the amount of force for

each of the Toftness adjustments.

Subjects in the control group followed the same

procedure as in the experimental group except chiropractic

adjustments were not given. The EMF readings in the

control group were taken before and after the Toftness

chiropractic assessments.

Body surface EMF was measured by the triaxial

fluxgate magnetometer FGM-5DTAA (FGM5DTAA)19

(Walker Scientific, Worcester, Mass) with 5-digit display.

The EMF can be displayed in nanotesla, microtesla, or

milligauss. The machine has a reported resolution of 1 nT

in a 100000-nT field. Thus, small variations in magnetic

field can be measured in the presence of a large field such

as the earth’s magnetic field. The FGM5DTAA instrument

has a sample rate of 69 samples per second for real-time

EMF measurement. The instrument was calibrated by

Walker Scientific before the study with a Certificate of

Calibration traceable to the National Institute of Standards

and Technology.

Fig 2. Cervical EMF changes in the control group.

Fig 8. Sacral EMF changes in the control group.Fig 4. Thoracic EMF changes in the control group.

Fig 6. Lumbar EMF changes in the control group.

Zhang and SnyderJournal of Manipulative and Physiological Therapeutics

Surface Electromagnetic FieldVolume 28, Number 3161

A Biopac MP 100 was used to record electrocardiogram

(ECG) and the R-R intervals necessary for HRV analysis

and computation of the SYMP and PARA. Disposable

electrodes (silver/silver chloride) were used for all bipolar

ECG measurements. The positive electrode was placed on

the left arm, the negative electrode was attached to the right

arm, and the ground electrode was placed on the right leg.

MP 100 amplifiers (model MP100; Biopac Systems, Inc,

Santa Barbara, Calif) were used for ECG amplification. All

postanalyses, including fast Fourier transforms, power

spectral density, and time domain measurements, were

performed with digital signal processing software. Heart

rate variability analysis was recorded once a week to

determine autonomic nervous system activity in both

control and experimental groups. Heart rate variability for

each subject was taken between 11:00 am and 12:00 noon

on each Monday or Wednesday.

All continuous data were expressed as mean F SD. A

repeated measurement analysis was used for the 6 visits

with the pre- and postcomparisons of continuous variables.

An a level of b.05 was considered significant.

RESULTS

In the cervical region, the force on the atlas vertebrae

ranged from a minimum force of 2 oz to a maximum of 8 oz,

and the time of the adjustments ranged from a minimum of

15 seconds to a maximum of 45 seconds in all of the

subjects. In the thoracic region, the force on the T5-T7 area

of the spine included a range from 4 to 12 oz, and the amount

of time ranged from a minimum of 10 seconds to a maximum

of 40 seconds in 8 of the subjects. Lumbar adjustments only

occurred in 2 of the subjects and the amount of force was

10 oz for 25 seconds in 1 of the subjects and 8 oz for 20 se-

conds in the other subject. Sacral adjustments also occurred

in all of the subjects and the amount of force ranged from a

minimum of 4 oz to a maximum of 12 oz, and the amount of

time for each adjustment ranged from a minimum of 20 se-

conds to a maximum of 45 seconds. As noted above, a cervi-

cal and sacral adjustment occurred in all of the 35 subjects.

Demographics of participants: among the 35 participants

in the study, 10 were women and 25 were men, ranging in

age from 23 to 58 years old. Among the 17 subjects in the

control group, there were 4 women and 13 men, with a

mean age of 26.2F3.8. Among the 28 subjects in the

experimental group, there were 6 women and 15 men with a

mean age of 27.7F6.3.

The EMF on the subjects’ body surface decreased at the

cervical, thoracic, lumbar, and sacral regions in all 6 visits

during the 4-week treatment period (Fig 1). There was a

downtrend of EMF over the 4-week period after Toftness

adjustment (Figs 1-8). The same changes were not observed

in the control group.

162 Journal of Manipulative and Physiological TherapeuticsZhang and Snyder

March/April 2005Surface Electromagnetic Field

The heart rate in the adjustment group had a slight

decrease over the 4-week treatment period. No heart rate

changes were observed in the control group over the same

period. HRV analysis did not find any consistent changes

before and after the low-force adjustments during the

treatment period.

DISCUSSION

It has been well documented that electrical current exits

at all muscle and nerve cells to maintain resting membrane

potential and action potentials.20 This electrical current

is easily measured on the body surface using the ECG

for recording electrical activities of the heart.21,22 Electro-

myogram (EMG) is another commonly used instrument

to determine the muscle electrical activities under varying

conditions.23,24

An EMF is produced whenever there is electrical current

flowing around the body. The EMF strength on the body

surface is determined to a large extent by the muscle mass and

nerves that supply the muscle fibers.25 This can be

demonstrated using a surface EMG on the forearm muscles.

The EMG tracing shows minimal deflections during resting

but shows maximal deflections as the muscles are engaged in

strenuous contractions. When the muscles fatigue, the

deflections on EMG tracing become reduced, indicating a

lowered electrical current across the muscle fibers. The

increase and decrease in electrical current are always

associated with the changing body surface EMF. Therefore,

it is certain that EMF exists on the body surface. However, it

has not been previously determined whether or not a Toftness

chiropractic adjustment affects the EMF of the body surface.

No studies have been done on the effect of chiropractic

adjustments on body surface EMF. Possible sources of body

surface EMF may come from the following: (1) electrical

current brought in and out of cells by K+, Na+, and Ca2+;

(2) the electrical current at a cellular level; (3) the muscle

mass of a human subject. However, it is possible that the

relaxation of muscles after chiropractic adjustment may

cause changes in EMF. Relaxation of muscles reduces the

electrical deflections that are closely correlated with lower

body surface EMF.26 It is also quite possible that relaxation

of muscles causes a decrease in the electrical current around

the cells leading to reduction of EMF on subjects’ body

surfaces. This is supported by a recent study that high-

strength EMF reduced sleep effectiveness.27

A reduction of EMF in the cervical, thoracic, lumbar, and

sacral regions after adjustments was seen in the experimen-

tal group for all 6 visits. No such systematic changes were

observed in the control group, which gives credence to the

validity of the measurement as indicative of what happens

during the adjustment procedure. Although fluctuations of

body surface EMF were seen during the 6 visits, exper-

imental subjects showed an overall trend of reduction in

EMF from the beginning of the study in the cervical and

thoracic regions. It should be noted that the low-force

adjustments were given in most cases to the cervical region.

This factor may contribute to the finding that the cervical

region was the area that showed consistent changes after a

chiropractic adjustment. The EMF readings in the thoracic,

lumbar, and sacral regions were similar to the cervical EMF

with an overall down trend in body surface EMF. These

findings are similar to a previous report by Toftness7 that the

cervical region is the area of highest sensitivity using the

stated analytical procedures.16 It was possible that this EMF

reduction at the cervical region was related to more frequent

chiropractic adjustments at this area. It will be interesting to

further investigate the role of frequency of chiropractic

adjustments on body surface EMF.

CONCLUSION

Normal human subjects showed a decrease in body

surface EMF in the cervical, thoracic, lumbar, and sacral

regions consistently after each session and cumulatively

after 4 weeks of the low-force chiropractic adjustments. The

mechanism of the reduction of body surface EMF is not

understood, but it might partially be because of relaxation of

the surrounding muscles.

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