Altered consciousness in flotation-REST and chamber-REST: Experience of experimental pain and subjective stress

Abstract

Twenty-three sportsmen were given one 45-minute exposure to flotation-REST and one exposure to chamber-REST on two occasions, incorporating random assignment to either flotation-REST followed by chamber-REST or vice versa. On each occasion, the Restricted Environmental Stimulation Technique (REST) procedure was followed immediately by testing experimentally induced pain to one arm using a blood pressure cuff. It was found that flotation-REST induced a significantly higher degree of altered states of consciousness (ASC), as measured with an instrument assessing experienced deviation from normal state (EDN), than did chamber-REST. Participants experiencing High EDN in the flotation-REST condition reported higher levels of both “experienced pain” and “experienced stress” than did those experiencing Low EDN. These results suggest that the particular distinguishing features of flotation-REST and chamber-REST may cause selective deviations from normal levels of consciousness, under experimental conditions, that may underlie the subjective experience of pain and stress thresholds.

Full text

ALTERED CONSCIOUSNESS IN FLOTATION-REST AND
CHAMBER-REST: EXPERIENCE OF
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS
ANETTE KJELLGREN, ULF SUNDEQUIST, ULLA SUNDHOLM AND
TORSTEN NORLANDER
Karlstad University, Sweden
TREVOR ARCHER
Göteborg University, Sweden
Twenty-three sportsmen were given one 45-minute exposure to flotation-REST and one
exposure to chamber-REST on two occasions, incorporating random assignment to either
flotation-REST followed by chamber-REST or vice versa. On each occasion, the Restricted
Environmental Stimulation Technique (REST) procedure was followed immediately by
testing experimentally induced pain to one arm using a blood pressure cuff. It was found that
flotation-REST induced a significantly higher degree of altered states of consciousness
(ASC), as measured with an instrument assessing experienced deviation from normal state
(EDN), than did chamber-REST. Participants experiencing High EDN in the flotation-REST
condition reported higher levels of both “experienced pain” and “experienced stress” than did
those experiencing Low EDN. These results suggest that the particular distinguishing features
of flotation-REST and chamber-REST may cause selective deviations from normal levels of
consciousness, under experimental conditions, that may underlie the subjective experience of
pain and stress thresholds.
Experimental methods for studying pain processes may elucidate questions
arising in clinical pain research. For example, experimental pain studies may be
used to develop “coping” strategies as well as to evaluate the efficacy of these
strategies (Edens & Gil, 1995). Nevertheless, studies involving experimentally
SOCIAL BEHAVIOR AND PERSONALITY, 2004, 32(2), 103-116
© Society for Personality Research (Inc.)
103
Anette Kjellgren, Ulf Sundequist, Ulla Sundholm and Dr. Torsten Norlander, Department of
Psychology, Karlstad University, Sweden; Trevor Archer, Department of Psychology, Göteborg
University, Sweden.
Appreciation is due to anonymous reviewers.
Keywords: experimental pain, stress, flotation-REST, chamber-REST, EDN, sportsmen, altered states
of consciousness.
Please address correspondence and reprint requests to: Dr. T. Norlander, Department of Psychology,
Karlstad University, SE-651 88 Karlstad, Sweden. Phone: 46-54-7001178; Fax: 46-54-839165;
Email: <Torsten.Norlander@kau.se>

induced pain are severely limited in their capacity to model the pain experienced,
for example, in chronic pain conditions, since among restrictions the affective
component is missing generally in the experimental setting (Rang, Dale, & Ritter,
1999). Furthermore, whereas experimental pain is usually predictable, this is not
the case in chronic pain, as participants in a pain experiment may terminate the
study at any time in full knowledge that at no time are they at risk for tissue
damage (Edens & Gil).
Although several methods exist for induction of experimental pain, induced
ischemia (due to lack of oxygen) and cold-presser pain are considered methods-
of-choice as models of chronic pain condition (Rainville, Feine, Bushnell &
Duncan, 1992). In the latter case, the participant is required to submerge his/her
hand into a bucket of ice water whereas in the former ischemic pain is induced
by elevating pressure at the blood pressure cuff on the participant's arm. In
ischemic pain, lack of tissue oxygen at the cuff inhibits the sodium-potassium
pump thereby increasing extracellular K+concentrations which in turn depolarize
pain receptors with consequent impulse generation and perception of pain (Nisell
& Lundeberg, 1993). Lack of tissue oxygen leads also to bradykinin
accumulation, further reinforcing the pain (Nisell & Lundeberg, 1993; Rang,
Dale, & Ritter, 1999).
Measurement of pain intensity can be performed using a Visual Analog Scale
(VAS) from 0-100, which is expressed often as being the “gold standard” for
assessment of pain (Yarnitsky, Sprecher, Zaslansky, & Hemli, 1996), although
verbal descriptions are utilized too. Comparisons of VAS with verbal descriptor
techniques indicate that both methods are equally sensitive for quantification of
pain intensity and its affective component (Duncan, Bushnell, & Lavigne, 1989).
At present, there are only a few studies on human participants involving
experimental pain in combination with relaxation/stress-reduction, whereas there
are a substantial number of studies showing the analgetic effect of relaxation
when using flotation-REST on clinical pain (e.g., Kjellgren, Sundequist,
Norlander, & Archer, 2001). Flotation-REST (Restricted Environmental
Stimulation Technique) is a mild form of sensory deprivation where the
participant is comfortably floating on his/her back in a saline solution contained
in a dark, anechoic tank. In order to further reduce incoming sensory perceptions,
the participant wears earplugs and the saline water solution is heated to skin
temperature, thus reducing auditory and tactile stimulation. The method induces
a state of relaxation and stress-reduction (e.g. Norlander, Kjellgren, & Archer,
2001).
The studies that have been made with REST and pain relief have in common
the fact that they study an already existing, chronic pain which is present when
the REST-treatment is begun (Kjellgren et al., 2001). These studies in no way
claimed that the pain relief was to be explained by the elevation of the
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS
104

participant’s pain threshold, but rather noted that the participants experienced
attenuation of the existing pain over time as REST-treatments were continued.
The aim of this study was consequently to investigate whether or not the degree
or level of altered state of consciousness could be of importance for the
subjective experience of experimental pain induced when the participant was
already in a mild altered state of consciousness. In order to practically achieve
this altered state of consciousness; sensory deprivation was used in a flotation-
REST tank and on a couch in a dark, silent room (chamber-REST), respectively.
METHOD
PARTICIPANTS
The study was carried out during two weeks, with a six-week interval
separating each week, at the Human Performance laboratory at Karlstad
University (Karlstad, Sweden). Twenty-three sportsmen were recruited through
association with sports-active groups in the province of Värmland (Sweden).
Their mean age was 29.48 years (SD = 4.97, range = 21 to 41), and 13 individuals
were students whereas 10 had professions. The participants reported that they
performed some form of sports activity at least 353.48 minutes per week (SD =
265.63). Sixteen participants had never smoked, 4 participants smoked only on
special occasions, like parties, and only 3 participants were regular smokers.
In order to obtain further background data two Hospital Anxiety and
Depression scales (HAD, Herrmann, 1997) were applied. The mean values for
HAD were: for the depression scale: 2.17 points (SD = 1.59), and for the anxiety
scale: 4.91 points (SD = 2.19), which may be compared with the clinical
boundary of 6 points for evidence of both depression and anxiety.
The participants received the pain induction procedure on two occasions (see
“Design”) and on both occasions had experienced pain prior to arrival at the
laboratory, which was estimated on a 100-degree scale (where 0 = no pain, 100
= intensive pain). Mean values on the first occasion were estimated to be 10.08
(SD = 16.36) and on the second occasion 8.00 (SD = 14.72), a difference that was
not found to be significant (paired-samples t-test, p= 0.413).
DESIGN
Each participant received a chamber-REST treatment and a flotation-REST
treatment. There was a 6-week interim period between the two REST treatments
and the order of treatment was randomized. Directly after the REST treatment,
degree of altered consciousness was measured as well as experienced time of the
REST treatment. On both occasions, the participants received the pain induction
procedure directly after the REST treatment. During the pain induction
procedure, measurements of experienced pain, experienced stress, pulse, and
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS 105

blood pressure were made. Directly after the pain induction procedure, the
experienced time of pain induction was estimated by the participant. For analysis,
a paired samples design (chamber-REST versus flotation-REST) was applied in
some analysis and in other analysis an independent samples design was used
whereby the dependent variables were analyzed within each respective REST
condition with Altered state of consciousness (Low, High) as the independent
variable.
INSTRUMENTS
(a) Flotation tank. Aflotation tank (Aqua-Anima, Sweden) measuring 2700 mm
x 1500 mm x 1300 mm was used. The depth of water varied between 250 and
300 mm. The tank was insulated, partially in order to prevent incoming noise, but
also to maintain a constant temperature for both water and air within the tank.
Despite slight variation, water temperature was maintained at 34.2°C. The water
in the flotation tank was saturated with magnesium sulphate to a concentration of
1.3 g/ml (cc). In contrast to a sodium chloride solution, magnesium salts (also
called Epsom salts) are benign upon the skin surface. The salt does not irritate or
dry out the skin. The roof of the tank was horizontally hinged and could easily be
opened and closed by participants. Between participants, the water was filtered
and sterilized with UV-light, and hydrogen peroxide was regularly added to
ensure hygiene.
(b) Couch. Asimple couch overlaid with a soft mattress, dimensions: 2000 x 800
mm was placed in the dark, quiet, noise-insulated room that was assigned to
provide the chamber-REST condition.
(c) Pulsoxymeter. Ohmeda Biox 3700e. The apparatus consists of an ear probe
attached to one ear lobe. Oxygen gas saturation, SpO2, and pulse frequency may
be assessed. The ear probe was attached to a participant's ear lobe immediately
before the start of the pain induction procedure. Registration of pulse and oxygen
saturation occurred 2, 5, 8, 10, 12, 13, 14 and 15 minutes after pain induction.
(d) Sphygmo manometer. Blood pressure cuff (Umedico, Sweden) as well as a
10-cm broad rubber band (Dauer, Sweden).
(e) Questionnaire 1. Background variables and Exclusion criteria. The
participants' expectations concerning flotation and eventual bodily responses to
pain were estimated on a VAS (0 - 100). Furthermore, questions regarding age
and tobacco as well as education, occupation and sports and exercise were
responded to. Additionally, participants responded “yes” or “no” to questions
pertaining to a) skin problems, cuts, bruises or any other complaints, b) any acute
or chronic illness, c) whether or not one was taking medication, and, d) whether
or not one suffered from any psychological problem. If a participant responded
with “yes”, the physician with medical responsibility made an examination to
decide whether or not the participant needed to be excluded.
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS
106

EXPERIMENTAL PAIN AND SUBJECTIVE STRESS
(f) Hospital Anxiety Depression Scale (HAD). The validity and reliability of the
HAD-scale for assessing degree of anxiety and depression symptoms has been
examined by Herrmann (1997). The HAD-scale measures the degree of anxiety
and depression wherein values under 6 are considered normal, those between 6
and 10 are assessed as being borderline and all values over 10 points are
indicative of a probable depression-anxiety diagnosis.
(g) Experienced deviation from normal state (EDN). Utilizing the interna-
tionally applied psychometric instruments APZ-questionnaire and OAVAV
(Dittrich, 1998) for obtaining judgments of altered states of consciousness, a
shortened but similar instrument was modified for use with flotation-REST
(Kjellgren et al., 2001). The APZ- and OAVAV-forms are the internationally
applied standard for this purpose and these tests have been validated in several
studies over different countries (Dittrich, 1998). In total, the EDN consists of 29
questions the answers to which are given on a VAS (0-100). The major portion of
these data is not applicable to the present study, so only a part of the test form
results are presented here. A complete “index of experience” was constructed
from the points obtained from all 29 questions which were averaged to provide a
“sum of experience”. These values ought to reflect the total experience of
deviation from normal states (EDN).
(h) Visual Analog Scale (VAS). This scale was used for measuring pain and
stress. The scale consists of a 10-cm horizontal line with the anchors no pain on
the left extreme and excruciating pain on the right extreme. As Yarnitsky et al.
(1996) point out: “VAS is considered the “gold standard” for assessment of
clinical and suprathreshold experimental pain, and changes in VAS score are
regarded as significant evidence of individual response to treatment, placebo, or
experimental manipulation”. The accuracy and precision have been examined for
both clinical and experimental pain, and found adequate (Price, 1988).
(i) Final Questionnaire. On arrival for the third visit at the laboratory, each
participant was asked about bodily pains, as well as his experience of remaining
complaints after the prior occasion's induction of pain.
PROCEDURE
Twenty-four sportsmen were recruited through contacts with the sports
community of Värmland County (Sweden) as participants in this study. On the
occasion of the first meeting, each participant was provided with information
about how the study was set up and told that it was possible to terminate
participation at any time. Questionnaires with background data and exclusion
criteria were assembled and collected and the participants responded to the HAD-
test. Afterwards, each participant was shown the procedure by which
experimental pain would be induced on the next occasion. An ordinary blood
pressure cuff was applied to each participant’s nondominant arm. Systolic blood
107

pressure was measured. The participant was then asked to hold his arm in an
upright position for 2 minutes, and at the same time to keep all his fingers
outstretched. After this, the arm (still upright) was bound hard with a rubber band
(the so-called Dauer binding) in order to constrict blood circulation from the
fingers to the point where the as-yet-deflated blood pressure cuff was applied.
Then the participant’s arm was allowed to descend to a normal resting position
on the table. Following this, the blood pressure was pumped up to double the
systolic blood pressure that had been measured earlier (normally about 250 mm
Hg). It was at this point that the actual pain induction (as performed in all the
following tests) was initiated, but during this introductory occasion the
demonstration was terminated by instead releasing the air from the cuff and
removing the rubber band. After this, the laboratory and flotation tank were
shown to the participant who was asked to use the lavatory and shower before
floating and shown how to insert the earplugs before going into the tank.
Following this, a test flotation over 20 minutes was given. Later, after showering
and dressing the participant was randomly assigned, for his next visit, to either
the flotation-REST or chamber-REST condition. Then the dark, quiet room with
the couch for chamber-REST was shown and the next visit of the participant was
booked.
On arrival for his second visit, the participant experienced either flotation-
REST or chamber-REST for 45 minutes, according to the condition to which he
had been randomly assigned. Flotation-REST procedures were maintained as
described above. The chamber-REST procedure was preceded by a toilet visit
and a change to comfortable clothes (T-shirt and underpants). On completion of
flotation-REST, the participant was allowed 15 minutes for showering and
changing. In order to ensure a similar temporal arrangement for chamber-REST,
the participant was required to remain in the room a further 15 minutes. After
completion of the respective REST-treatment the participant was required to
complete the EDN-test. After this, the induction of pain procedure was initiated.
The same procedure was completed, as described earlier, during the first visit as
well as the careful attachment of the pulsoxymeter and ear-probe to the
participant’s ear. Paper and coloring pens were available on a table in front of the
participant and he was urged to “draw something” with his free arm during the
time that the induction of pain procedure was maintained.
Measures of experienced pain were taken, by questioning, then every minute
(which the participant marked on the horizontal line on the VAS-scale, whereby
0 indicated no pain and 100 indicated excruciating pain). Degree of “experienced
stress” was estimated, by questioning, at 2, 5, 8, 10, 12, 13, 14 and 15 minutes,
here too the VAS-scale was used whereby 0 indicated not stressed at all and 100
indicated maximum possible stress. Concurrently with the participant’s
estimations of experienced stress, pulse frequency and oxygen levels were
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS
108

measured using the pulsoxymeter. The participants had not received any
information about how long the experiment could continue but rather, were
instructed to carry on as long as they were able to. After 15 minutes the cuff was
removed and the experiment terminated. As part of the experiment it was decided
that the experimenter would terminate the experiment if any participant estimated
“experienced pain” on the VAS-scale between 75-80 or more, or if some aspect
of the verbal communication between the experimenter and the participant
indicated that the individual was unnecessarily troubled by pain. However, this
situation did not occur for any of the participants. Immediately after the cuff had
been removed, the participant was required to estimate the length of time that it
had remained inflated upon his arm.
On arrival at the laboratory for the third and final visit, the participant was
required to complete a questionnaire containing questions about bodily pain and
eventual discomfort following previous induction of pain. After this, the
experiment was carried out in an identical manner to the procedure used during
the participant’s second visit to the laboratory except that the other REST-
condition, compared to that applied in the previous visit, was presented. On
completion of the experiment the participants were each thanked for their
participation.
RESULTS
DATA REDUCTION
In order to facilitate the statistical analysis, the possibility of performing
reduction of the data regarding experienced pain, experienced stress, pulse rate
and oxygen saturation was investigated by regression analysis (enter-method)
through calculating Multiple R (R).
The analyses indicated significant correlations for experienced pain following
couch (R= 0.99, p = 0.002) and following flotation tank (R= 0.99, p< 0.001),
for experienced stress following couch (R= 0.94, p< 0.001) and following
flotation tank (R= 0.96, p< 0.001), for pulse rate following couch (R= 0.91,
p< 0.001) and following flotation tank (R= 0.95, p< 0.001), as well as for
oxygen saturation following couch (R= 0.91, p< 0.001) and following flotation
tank (R= 0.93, p< 0.001). Since these analyses indicated high correlation values
(R> 0.90), the mean values for the results pertaining to experienced pain,
experienced stress, pulse rate and oxygen saturation in exhaled air were applied
to further statistical analysis.
COMPARISON BETWEEN CHAMBER-REST AND FLOTATION-REST
In order to analyze the dependent variables, statistics with Paired Samples t-test
(5% level) were used. The analyses did not indicate any significant differences
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS 109

between chamber-REST and flotation-REST with regard to experienced pain (p
= 0.989), experienced stress (p= 0.985), pulse rate (p= 0.293), blood pressure (p
= 0.476), oxygen saturation in blood (p= 0.316), estimated time for REST-
treatment duration (p= 0.086), and estimated time for blood pressure cuff
duration (p= 0.966). However, there was a significant difference with regard to
altered state of consciousness (EDN) [t(22) = 4.88, p< 0.001], whereby it was
indicated that flotation-REST induced a higher degree of altered state of
consciousness (M= 32.48, SD = 15.94) compared with the chamber-REST
condition (M= 15.10, SD = 13.11). Table 1 presents the means and standard
deviations for each variable in the flotation-REST and chamber-REST
conditions.
COMPARISON BETWEEN LOW AND HIGH EDN WITHIN RESPECTIVE REST
CONDITION
The participants’ points regarding altered state of consciousness (EDN)
following the chamber-REST treatment were divided to form two groups (cut-
off-point = 47.8 %), that is, one group presenting a low altered state of
consciousness (Low EDN, 11 individuals, M= 4.98, SD = 2.12) and one group
presenting a high altered state of consciousness (High EDN, 12 individuals, M=
23.36, SD = 12.69). An identical procedure was applied to participants’ points
regarding altered level of consciousness (EDN) following the flotation-REST
treatment in that they were divided to form two groups (cut-off-point = 47.8 %),
with one group presenting a Low EDN (11 individuals, M= 19.29, SD = 7.23)
and the other group presenting a High EDN (12 individuals, M= 44.58, SD =
12.26).
Chamber-REST. Independent Samples t-tests (5% level) with EDN (Low, High)
as independent variable did not indicate any significant differences between low
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS
110
TABLE 1
MEANS (AND STANDARD DEVIATIONS) FOR THE VARIABLES PERTAINING TO THE REST-
CONDITIONS
Chamber-REST Flotation-REST %Quotient
Experienced pain 26.92 (15.63) 26.88 (18.37) 100
Experienced stress 11.61 (12.42) 11.65 (13.30) 100
Pulse 69.26 (11.01) 70.77 (10.90) 102
Blood pressure 108.26 (12.76) 111.09 (10.76) 102
Experienced REST-time 36.17 (8.05) 41.89 (10.06) 116
Experienced cuff time 10.08 (2.89) 9.46 (2.96) 94
EDN * 14.57 (13.06) 32.48 (15.94) 223
Notes: * indicates significant difference (5% level) between REST-conditions.
% Quotient was derived by dividing Flotation-REST mean values by chamber-REST mean value and
multiplying by 100.

and high degree of altered state of consciousness regarding experienced pain (p
= 0.073), experienced stress (p= 0.110), pulse rate (p= 0.762), blood pressure (p
= 0.410), oxygen saturation in blood (p= 0.462), estimated time for REST-
treatment duration (p= 0.443), or estimated time for blood pressure cuff duration
(p= 0.355). Table 2 presents the means and standard deviations between Low and
High EDN in the chamber-REST condition.
Flotation-REST. Independent Samples t-tests (5% level) with EDN (Low, High)
as independent variable did not indicate any significant differences between low
and high degree of altered state of consciousness levels regarding pulse rate (p=
0.820), blood pressure (p= 0.156), oxygen saturation in blood(p= 0.192), and
estimated time for REST-treatment duration (p= 0.191). However, there was a
significant difference with regard to experienced pain [t(21) = 3.59, p= 0.002],
whereby further analysis indicated that the participants presenting High EDN
experienced a higher level of pain (M= 37.49, SD = 18.84) compared with those
presenting a Low EDN (M= 15.30, SD = 8.30). Furthermore, there was a
significant difference with regard to experienced stress [t(21) = 2.23, p= 0.037],
whereby further analysis indicated that the participants presenting High EDN
experienced a higher level of stress (M= 17.10, SD = 16.06) compared with those
presenting a Low EDN (M= 5.70, SD = 5.54). Finally, there was a significant
difference with regard to estimated time for blood pressure cuff duration [t(21) =
3.057, p= 0.010], whereby further analysis indicated that the participants
presenting Low EDN experienced a longer duration of blood pressure cuff (M=
12.00, SD = 2.74) compared with those presenting a High EDN (M= 8.00, SD =
2.07). Table 3 presents the means and standard deviations between Low and High
EDN in the flotation-REST condition.
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS 111
TABLE 2
COMPARISONS BETWEEN THE LOW-EDN AND HIGH-EDN REPORTING PARTICIPANTS WITHIN THE
CHAMBER-REST CONDITION
Low-EDN High-EDN %Quotient
Experienced pain 20.84 (7.50) 32.49 (19.15) 155
Experienced stress 7.27 (6.04) 15.58 (15.46) 214
Pulse 70.01 (7.69) 68.57 (13.70) 98
Blood pressure 105.91 (13.75) 110.42 (11.96) 104
Experienced REST-time 34.57 (7.16) 38.40 (9.50) 111
Experienced cuff time 9.38 (2.83) 10.72 (2.97) 115
EDN * 4.98 (2.12) 23.36 (12.69) 469
Notes: * indicates significant difference (5% level) between High and Low EDN.
% Quotient was derived by dividing High-EDN mean values by Low-EDN mean value and
multiplying by 100.

DISCUSSION
In the present study, twenty-three male athletes participated in two REST
conditions (chamber, flotation), wherein the order of presentation of the
conditions was randomized, but the time interval between each REST condition
was held constant, that is, six weeks. One main finding was that flotation-REST
induced a significantly higher degree of altered states of consciousness (ASC), as
measured with EDN, than chamber-REST. This finding confirms the results of
earlier studies (e.g., Norlander, Kjellgren, & Archer, in press). In this study the
experience of an ASC is described in terms of a continuum of the two REST
conditions by which participants achieving a “higher altered state” in the
Chamber-REST condition essentially displayed the same EDN points as did
those participants achieving a “lower altered state” in the flotation-REST
condition. Participants achieving higher ASC in the latter condition experienced
significantly more pain and stress, and also perceived pain duration as shorter
compared with those participants with a lower ASC in the same condition.
Comparison of lower and higher ASC in the chamber-REST conditions did not
produce such differences. Thus, it is possible that acute induced pain may be
experienced with more intensity under conditions wherein the higher levels of
ASC (as assessed by EDN) are associated with elevated levels of awareness and
sensitivity consciousness and sensitivity for sensory stimuli. It appears that the
hypothesis regarding the role of ASC in receptivity to acute pain was confirmed.
As indicated previously, an ASC is marked by increased focus and attention upon
internal stimuli and processes (Ludwig, 1990). Nevertheless, it does not appear
that the role of ASC in acute induced pain has been addressed previously. With
regard to chronic pain, several studies have shown that flotation-REST induced
an alleviation of pain (e.g., Kjellgren et al., 2001).
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS
112
TABLE 3
COMPARISONS BETWEEN THE LOW-EDN AND HIGH-EDN REPORTING PARTICIPANTS WITHIN THE
FLOTATION-REST CONDITION
Low-EDN High-EDN %Quotient
Experienced pain* 15.30 (8.30) 37.49 (18.84) 245
Experienced stress* 5.70 (5.54) 17.10 (16.06) 300
Pulse 71.33 (10.09) 70.26 (12.06) 98
Blood pressure 107.73 (8.47) 114.17 (12.03) 106
Experienced REST-time 39.27 (9.21) 45.50 (10.66) 116
Experienced cuff time* 12.00 (2.74) 8.06 (2.07) 67
EDN * 19.29 (7.23) 44.58 (12.26) 231
Notes: * indicates significant difference (5% level) between Low and High-EDN.
% Quotient was derived by dividing High-EDN mean values by Low-EDN mean value and
multiplying by 100.

Certain cognitive relationships may underlie the influences of Flotation-REST
upon acute and chronic pain, respectively. REST appears to induce a “cognitive
shift” (Norlander, Bergman, & Archer, 1998) whereby primary process thinking
(i.e., “here and now” thinking) is reinforced at the cost of secondary process
thinking (i.e., a more “abstract and temporal-based” thinking). It is possible that
under the influence of heightened primary process thinking, for example, through
the Flotation-REST experience, an individual with an existing pain (chronic)
experiences greater attention upon physical and psychological relaxant effects
accompanied by reduced attention upon the pain signal. Conversely, if an
individual not bearing any particular pain experience directly after Flotation-
REST is exposed to intense pain he/she may experience intensive distress due to
the abrupt termination of primary process thinking. Previous studies (Norlander
et al., 1998) have demonstrated an “after-effect” whereby elevation of primary
process remains for at least an hour after flotation. Possibly, the stronger the
influence of primary process the greater the distress due to enforced “cognitive
shift”.
The application of intense experimental pain in the present study distinguishes
it from other REST studies. Furthermore, all the participants were aware that the
experimental pain would not cause lasting damage, and that the pain would end
when the experiment was terminated or when they themselves, as free volunteers,
chose to terminate. These considerations indicate that the affective components
otherwise associated with chronic pain were missing (as discussed earlier, this is
one of the weaknesses of experimental pain studies). Further, it ought to be noted
that the present study incorporated a single instance of REST-Flotation rather
than a series of treatments as applied in the previous pain-reduction studies
wherein different types of neurohumoral and/or physiological changes may have
occurred and to some extent been measured (Kjellgren, et al., 2001).
The present study suggests the existence of some “threshold-level” in the
degree of ASC that must be overcome before measurable effects on the variables
investigated are observed. The finding that degree of experienced ASC in the
chamber-REST condition induced means for the highest EDN values (i.e., most
altered) that were comparable to those of the lowest EDN values for Flotation-
REST seems to support this notion. Note that the means of the highest EDN
values (ASC) for flotation-REST are much higher (High-EDN as a percentage of
Low-EDN: Experienced pain = 245%, and Experienced stress = 300%) than
those of the highest EDN values for chamber-REST (High-EDN as a percentage
of Low-EDN: Experienced pain = 155%, and Experienced stress = 214%). It
ought to be indicated that there were no significant differences for experienced
pain and stress on the comparison between the methods, flotation-REST and
chamber-REST, but rather the significantly higher pain and stress experiences
were reported from individuals showing the highest ASC values.
EXPERIMENTAL PAIN AND SUBJECTIVE STRESS 113

One characteristic property of ASC is disturbance of temporal perspective
(Ludwig, 1990). It was found that the experience of time during which pain was
applied (cuff-duration) was significantly different for participants expressing a
high degree of ASC within the flotation condition. Previous flotation-REST
studies (Norlander, Kjellgren, & Archer, 2001) have shown too that, for
individuals under the influence of the flotation tank experience, time passes more
quickly. The shortened time perspective by the High-EDN participants in the
Flotation-REST condition (High-EDN as a percentage of Low-EDN:
Experienced cuff duration = 67%) compared to Low-EDN participants may offer
further effects of the condition that may be pertinent to the more intensive
experience of pain. In the chamber-REST condition, the High-EDN participants
indicated a slightly, but nonsignificantly, lengthened time perspective (High-
EDN as a percentage of Low-EDN: Experienced cuff duration = 67%) compared
to Low-EDN participants.
It is possible that a different group of participants may have provided a
different set of results. The pain experience in an experimental pain method may
also be modulated by the type of instructions provided to participants. Here, the
instruction was: “try to withstand the pain as long as you are able to” instead of
informing the participants that pain was to be experienced during a fixed time
duration (in this case 15 minutes). Thorn and Williams (1989) have shown that
estimations of pain in ischemic pain tests are lower if participants are given prior
information that the pain was of fixed duration. The “fixed-time” instruction was
withheld in order to provide a semblance of clinical pain wherein an uncertainty
regarding duration of pain is probably a factor of some influence.
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