Effects of Soft Tissue Mobilization
(Rolfing Pelvic Lift) on Parasympathetic Tone in Two Age Groups
JOHN T. COTTINGHAM, STEPHEN W. PORGES, and
TODD LYON
First published in ‘Physical Therapy’, Vol.
68, No. 3, March 1988
Journal of
American Physical Therapy Assn.’
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The effects of a soft tissue mobilization procedure, the Rolfing pelvic lift, on parasympathetic tone was studied in healthy adult men. Parasympathetic tone was assessed 1) by quantifying the amplitude of the respiratory sinus arrhythmia from the heart rate pattern and 2) by measuring heart rate. Heart rate patterns were assessed during the pelvic lift and during the durational touch and baseline control conditions. Two groups of healthy subjects were tested: Group 1 contained 20 subjects aged 26 to 41 years, and Group 2 contained 10 subjects aged 55 to 68 years. In Group 1, the pelvic lift elicited a somatovisceral‑parasympathetic reflex characterized by a significant increase in parasympathetic tone relative to durational touch and baseline conditions. Group 2 did not exhibit a parasympathetic change during the pelvic lift. The results of this study contribute to our understanding of pelvic mobilization techniques and may help to explain why these techniques have been clinically successful in treating myofascial pain syndromes and other musculoskeletal dysfunctions characterized by reduced parasympathetic tone and excessive sympathetic activity.
Key Words: Autonomic
nervous system; Cardiac, general; Manual therapy; Physical therapy.
J, Cottingham, MS, is
Certified Advanced Rolfing Practitioner, Staff Manual Therapist, and Research
Associate, Frances Nelson Health Center, 1306 Carver Dr, Champaign, IL 61820
(USA).
S. Purges, PhD, is
Director, Developmental Assessment Laboratory, and Professor, Department of
Human Development, College of Education, University of Maryland at College
Park, College Park, MD 20742.
T. Lyon, MD, is Medical Director,
Frances Nelson Health Center, and Associate Instructor of Family Practice
Medicine, College of Medicine, University of Illinois, 190 Medical Science
Bldg, 506 S Mathews Ave, Urbana, IL 61801.
This research was
supported in part by a basic research grant from the Rolf lnstitute to the
Frances Nelson Health Center.
This article was
submitted January 15, 1987; was with the authors for revision four weeks; and
was accepted June 22, 1987. Potential Conflict of Interest: 4.
Mobilization of the bony pelvis and the surrounding soft tissues has
been used in medical practice since the beginning of recorded history, Ancient
Chinese, Egyptian, and Greek medical accounts all describe pelvic manipulations
and associated changes in breathing, arterial pulse, body temperature, and
muscle tone.(1) Several schools of manual therapy, including chiropractic,
osteopathic, and Rolfing, have rediscovered and further developed these
mobilization practices in the United States in the last century.(2‑4) A
resurgence of interest in soft tissue manipulative techniques is evident in the
physical therapy and medical literature of the last two decades.(5-7) Advocates
of these techniques have recommended pelvic mobilization for various clinical
problems that involve autonomic nervous system (ANS) dysfunctions.
Scientific evaluation of soft tissue manipulative treatments is
difficult because of the scarcity of experimental studies, the difficulty in
quantifying treatment outcomes, and the speculative nature of the
neurophysiological mechanisms of ANS action.(8,9) Homogeneous subject samples
undergoing standardized treatment procedures must be examined to establish the
ANS responses associated with a given manipulation. Such information will allow
more appropriate selection of manual therapy for specific conditions.
This study examined the pelvic lift mobilization procedure and
associated changes in ANS tone. Pelvic lift is a soft tissue manipulation from
the Rolfing method of manual therapy and movement education. It involves a combination
of posterior tilting and pelvic traction with concurrent moderate pressure to
the epigastrium. (4,10) Lumbosacral decompression, a similar technique, is
involved in osteopathic manipulative techniques.(11) Both the pelvic lift and
the lumbosacral decompression maneuvers have been associated with an increase
in parasympathetic nervous system (PNS) tone and a corresponding decrease in
sympathetic nervous system (SNS) activity.(10,11)
Pelvic lift also is comparable to the facilitated pelvic tilt exercise
described in the physical therapy and occupational therapy literature. (12,13)
The pelvic tilt originally was devised by Paul Williams as part of a series of
back exercises.(13) The facilitated pelvic tilt and related pelvic mobilization
techniques, however, currently are used with adults, children, and infants in
various therapeutic contexts: 1) to
activate selected thoracic and abdominal breathing patterns,(1,14) 2) to inhibit hyperactive behaviors,
(1,14) 3) to inhibit shoulder
elevation and retraction (14‑17) 4)
to reduce hyperextensive neck and back patterns (6,7,15‑17) and 5) to reduce chronic soft tissue pain
associated with excessive SNS activity. (1,14,16,17) The posterior pelvic tilt
has been demonstrated to reduce electromyographic activity in the lumbosacral
regions of healthy young adults when compared with anterior pelvic tilt and
baseline measurements.(13)
The results of experimental investigations of ANS reflexes and tactile
stimulation also support the clinical observations that pelvic mobilization
appears to be correlated with increased PNS activity. Overall, the studies
indicate that deep mechanical pressure to the abdominal region, slow stroking
to the back, and sustained pressure to the pelvis produce increases in PNS
reflex responses, including increased electrical activity in sacral and vagal
fibers increased peripheral skin temperatures, synchronous
electroencephalographic patterns. and decreased EMG activity.(14‑22) These
studies have also demonstrated that autonomic and somatic responses are
integrated, not two independent motor systems. (22)
Age also appears to be an important
factor in determining the responsiveness of the ANS of human subjects to a
given stimulus (eg, tactile). Studies on aging have demonstrated that subjects
over 60 years of age show slower and diminished ANS than younger subjects. (23)
We decided to measure PNS tone in
this Study because tactile stimulation of the pelvis, back, and abdominal regions
enhances PNS activity. The method we selected to assess PNS activity involved
the analysis and isolation of rhythmic variations in the heart rate pattern
that are correlated with PNS cardiac innervation through the vagus nerve,
Katona and Jih.(24) in a study of anesthetized dogs. and Eckberg, (25) in a
study of conscious human subjects. demonstrated that measuring the amplitude of
the heart rate oscillations associated with respiration could be used as an
index of cardiac PNS tone. Respiratory sinus arrhythmia (RSA) is the rhythmic
increase in heart rate associated with inspiration and the decrease in heart
rate associated with expiration (Fig. 1).
Complex mechanisms control the
relationship between RSA and cardiac vagal tone. Some cardiovascular physiologists
traditionally have considered RSA to be produced by nonneural factors rather
than by cardiac vagal reflexes. Strong evidence currently exists, however, that
respiration, through either a central mechanism or a peripheral feedback loop
to medullary areas, phasically inhibits, or "gates,"' the source
nuclei of the vagal cardioinhibitory fibers. (24‑27) Respiration is
involved in the phasic modulation of the vagal influences to the heart, with
the maximal inhibition occurring during the mid‑ to late‑inspiratory
phase and the maximal output occurring during the expiratory phase. (28‑31)
Because the vagal Cardioinhibitory neurons by definition slow the heart rate
and exhibit a respiratory frequency, their impact on heart rate should be a
slowing of heart rate during the expiratory phase of respiration, The greater
the vagal efferent output to the heart, the greater the slowing of heart rate
during expiration. Thus, RSA is a peripheral manifestation of the influence of
the vagal cardioinhibitory neurons on the heart (le, cardiac vagal tone), and a
strong argument can be made that quantification of the amplitude of RSA is an
accurate index of cardiac vagal tone. (32)
Porges developed a unique method of
accurately quantifying RSA with timeseries procedures. (33) This method of
assessing cardiac PNS activity has been validated experimentally.
Pharmacological and electrophysiological manipulations of cardiac vagal
efferent tone in rats, cats. and humans were found to be reliably reflected in
the amplitude of RSA. (32, 34‑36) Because of the direct relationship
between this method of quantifying RSA and cardiac PNS tone, the statistical
description of the RSA amplitude has been termed vagal tone.
The purpose of this study was to
examine the immediate PNS responses of two age groups of healthy male subjects
to 1) the application of a single soft tissue pelvic procedure, the Rolfing
pelvic lift, and 2) a control manipulative procedure involving sustained
tactile pressure, durational touch.
We formulated two hypotheses based
on the literature review. First, the pelvic lift would elicit a somatovisceral‑PNS
reflex and increase PNS tone, but the durational touch would not produce such
an increase. Second, a group of young, healthy male subjects would demonstrate
greater autonomic responsiveness (ie, larger increases in PNS tone) to the
pelvic lift than a group of older healthy male subjects.
METHOD
Subjects
Two groups of men were selected for
this study. Group I consisted of 20 healthy men aged 26 to 41 years (X = 32
years), and Group 2 consisted of 10 healthy men aged 55 to 68 years (X = 63
years). All subjects were nonsmokers and reported no known health problems. The
subjects were oriented to soft tissue therapy before testing. All subjects were
selected on a volunteer basis from the professional practice of the primary
investigator (J.T.C.). Each subject signed an informed consent form to
participate in the study. The study procedure was approved by the Frances
Nelson Health Center Board of Directors. Two subjects from Group I and one
subject from Group 2 were eliminated from the data analysis because of problems
with the ECG signal.
Materials
We placed electrodes bilaterally on
the ventral wrists of the subjects and monitored ECG activity with an ECG
amplifier.[1]
The output of the ECG amplifier was fed into a Vagal Tone Monitor[2]
a microcomputer that calculates vagal tone and heart rate. A quiet environment
was maintained with an average temperature of 24°C (range = 23°‑25°C).
Procedure
During each testing session before
data collection, the subjects were positioned supine on a treatment table with
the electrodes placed on their wrists. Five minutes was allowed for adaptation
to the environment. We gave the subjects instructions about the testing
procedure during this interval.
We monitored the subjects' ECG
activity during five consecutive three‑minute conditions: 1) baseline, 2)
manipulation, 3) baseline, 4) manipulation, and 5) baseline. The vagal tone
monitoring device was located in an adjacent room so that the investigator did
not have access to the heart rate data during the testing session. Fifteen
subjects experienced the pelvic lift manipulation first, and the other 15
subjects experienced the durational touch manipulation first. We administered
the pelvic lift with the subjects in a Supine position with their knees flexed.
The experimenter placed one hand under the subject's sacrum so that his
fingertips rested on the lumbosacral junction. He then applied traction to tilt
the pelvis in a posterior direction (ie, tilting the anterior superior spines
posterior to the pubic symphysis in the sagittal plane). The experimenter
placed his other hand on the subject's epigastrium with moderate pressure. The
control manipulation of durational touch involved moderate bilateral pressure
by the experimenter's hands to the subject's anterior deltoid muscles. The
manipulative techniques were administered by the primary investigator (J.T.C.),
a certified advanced Rolfing practitioner.
Data Quantification and Analysis
We assessed the dependent variables
of vagal tone and heart rate during sequential 30‑second periods within
each three‑minute condition. Heart rate in beats per minute was
calculated as; twice the number of interbeat intervals within each 30‑second
period. We calculated the vagal tone index by extracting the amplitude of RSA
from the beat‑to‑beat pattern. This procedure necessitated the
following steps: 1) conducting a timeseries analysis, I‑) applying a
moving polynomial filtering procedure that removes the heart rate variability
associated with baseline trends and periodic activity slower than respiration,
3) band‑pass filtering the residual series to allow only the heart rate
pattern 'in the frequency band associated with spontaneous respiration to pass,
4) calculating the variance of band‑pass series that represents the RSA
amplitude, and 5) calculating the natural logarithm of this variance to
normalize its distribution. (37)
We calculated analyses of variance
(ANOVAs) for vagal tone and heart period with age group and order of treatment
as between‑subject factors and treatment as a within‑subject
repeated measure.(37) An alpha level of .05 was used for statistical
significance.
RESULTS
For the dependent variable of vagal tone,
the ANOVA demonstrated a Significant group by treatment interaction (F = 2.7;
df = 4,92; p < .05) (Table).
Simple‑effects ‑post hoc tests of univariate ANOVAs For Groups 1 and 2 demonstrated that only Group I exhibited significant differences among the five treatment conditions (F = 12.5; df = 4,64; p < .0005). Examination of the treatment means and standard errors in Group I clearly indicated that this significant variance was related solely to the increase in vagal tone during the pelvic lift (Fig. 2). The control treatment of durational touch did not significantly influence vagal tone. A significant group effect (F = 8.4; df = 1,23; p < .01) that the young subjects in
Group I had a higher overall vagal
tone than the older subjects in Group 2.
Heart rate as a dependent variable
was not sensitive to the manipulations (Fig. 3). A significant group effect (F
= 7.7, df = 1,23; p < .05) demonstrated that the young Subjects in Group I
had a lower heart rate than the older subjects in Group 2. The order of
manipulation did not significantly influence the two dependent variables.
DISCUSSION
To our knowledge, this study
represents the first attempt to quantify the effects of a soft tissue
mobilization procedure on AN'S function tie, cardiac vagal tone) Linder
controlled conditions. The data clearly demonstrate that the Rolfing pelvic
lift produces an increase in cardiac vagal tone in young, healthy male
subjects. Neither durational touch nor the baseline conditions influenced the
level of PNS tone. The increased vagal tone during the pelvic lift returned to
the initial baseline level upon cessation of the maneuver, indicating that the
elicited response did not persist after removal of the stimulus. This finding
supports the initial hypothesis that a somatovisceral‑PNS reflex would be
elicited by the pelvic lift. (22)
The study results also demonstrate
that vagal tone is a more sensitive ANS index for assessing pelvic lift than
heart rate. This finding may be due to the specificity of the vagal tone assessment.
Vagal tone was defined as the component of the heart rate variability that is
associated with respiration's phasic modulation of the vagal cardioinhibitory
efferents (ie, RSA amplitude). (28‑32) Heart rate, in contrast, is a more
global ANS index of heart rate variability that involves PNS and several other
(eg, SNS, intrinsic, and mechanical) components. (32)
In the older age group, the pelvic
lift did not elicit an ANS response. This finding is supported by studies on
aging and ANS activity. Elderly subjects have shown more difficulty than
younger subjects in responding to changes in ambient room temperature and in
recovering resting pulse rate and respiratory volume after displacement by
exercise. (23) Subjects over 60 years of age also have exhibited less
predictability in the ANS reflexes that control heart rate, pupil size, and
gastrointestinal tract.(23) Other research has demonstrated that the aging
process is associated with less sudomotor activity (ie, sweating), progressive
increase in rigidity of the aorta and peripheral arteries, and reduced ANS
conditionability. (38) The older subject group may have exhibited reduced
sensitivity in receptor response to the tactile stimuli provided by the pelvic
lift. (23, 38) Another possible explanation, supported by the significantly
lower levels of vagal tone found in Group 2 than in Group 1, is that aging is
associated with a general reduction in brain stem cardiac vagal outflow, which
limits the somatovisceral‑PNS response to the pelvic lift.(26,27,32)
What aspects of the pelvic lift
account for its somatovisceral‑PNS consequences? The pelvic lift has two
distinct mechanical components: 1) moderate sustained pressure to the
epigastrium and 2) firm posterior tilting and traction to the pelvis.
Experimental studies on ANS reflexes have demonstrated that both deep pressure
to the abdominal region and tactile stimulation to the back and sacral nerve
roots produce PNS cardiovascular reflexes and alterations in respiratory
patterns. (14, 18‑20) Both mechanical components of the pelvic lift,
therefore, probably contribute to the somatovisceral‑PNS response.
Additional experimental investigation is needed to evaluate the relative
importance of the two mechanical elements and whether they act synergically to
elicit the observed somatovisceral‑PNS reflex.
Although we conducted this study on
healthy adults, the results have possible clinical implications, Our Finding
that the older subjects did not exhibit a vagotonic reflex response to the
pelvic lift implies that elderly clinical populations may not be as responsive
to soft tissue mobilization as younger populations. The assessment of a
patient's PNS tone to a given soft tissue procedure may provide a useful
criterion for determining the appropriateness of manual therapy.
Another clinical implication of'
this study pertains to the finding that in the younger subjects, pelvic lift
produced a transient increase in PNS tone. suggesting a relaxed, nurturing
physiological state. This finding contrasts with the heightened arousal and
"fight‑flight" activity associated with increased SNS
tone.(14,18) Furthermore, ANS investigations by Gellhorn have demonstrated a
general law of reciprocity: When one ANS division is excited, the other
division is inhibited to maximize the response of the stimulated branch.(18)
The increased PNS tone elicited by the pelvic lift in our study may be
associated with a corresponding reduction in SNS tone.
From a therapeutic perspective, this
combination of enhanced PNS activity and suppressed SNS tone may explain in
part the successful clinical reports of pelvic mobilization as a treatment
modality. (1,6,7, 14‑17) Such an ANS response would indicate favorable
conditions for the reduction of muscle spasm and peripheral vasoconstriction
commonly correlated with myofascial pain syndromes (eg, primary fibromyalgia).
(39) Other musculoskeletal disorders in infants, children, and adults that
involve autonomic stress Lee, chronic SNS) may benefit from pelvic
mobilization, including the treatment of restricted breathing patterns,
hyperactive behaviors, and hyperextensive neck and back patterns.(40)
We must emphasize, however, that
this study demonstrated only a transient, reflexive increase in vagal tone in
young, healthy adults to a single pelvic mobilization technique. The long‑term
ANS effects of pelvic lift and other soft tissue mobilization techniques can be
established on a scientific basis only through additional research. We
currently are designing a study that will compare two matched groups of healthy
adults. One subject group will receive a sequence of Rolfing sessions. and the
other group will receive a series of control treatments We will assess both ANS
activity and joint range of motion.
CONCLUSION
With a group of Voting, healthy adult male subjects a soft tissue
mobilization procedure, Rolfing pelvic lift, was found to significantly
increase PNS tone (car diac vagal tone) for the duration of the manipulation,
followed by a return of vagal tone to baseline levels. A control manipulation,
durational touch, pro duced no change in PNS tone. A second group of older,
healthy male subjects did not demonstrate a significant vagotonic response to
pelvic lift. Possible neurophysiological mechanisms of the pelvic lift effect
were discussed in terms of a somatovisceral‑PNS reflex.
The increase of PNS tone produced by
the pelvic lift in the group of younger subjects and the probable concurrent
reciprocal Inhibition of SNS tone may explain why pelvic mobilization
techniques have been used successfully in various clinical applications for
musculoskeletal disorders associated with ANS dysfunction.
Acknowledgments. We thank Gregory A.
Miller, PhD, Department of Psychology, University of Illinois at Urbana‑Champaign,
for his assistance in developing the experimental design and Georgia DeGangi,
MS, ORT, Department of Psychology, University of Maryland at College Park, for
her comments and suggestions in preparing this manuscript.
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