A Test of the Independent and Interactive Effects of Domain-Specific Awareness and
Acceptance Manipulations on Cardiovascular Responses to Acute Stress
A dissertation presented to
the faculty of
the College of Arts and Sciences of Ohio University
In partial fulfillment
of the requirements for the degree
Doctor of Philosophy
Andrew W. Manigault
May 2020
© 2020 Andrew W. Manigault. All Rights Reserved. 2
This dissertation titled
A Test of the Independent and Interactive Effects of Domain-Specific Awareness and
Acceptance Manipulations on Cardiovascular Responses to Acute Stress
by
ANDREW W. MANIGAULT
has been approved for
the Department of Psychology
and the College of Arts and Sciences by
Peggy M. Zoccola
Associate Professor of Psychology
Florenz Plassmann
Dean, College of Arts and Sciences 3
Abstract
MANIGAULT, ANDREW W., Ph.D., May 2020, Psychology
A Test of the Independent and Interactive Effects of Domain-Specific Awareness and
Acceptance Manipulations on Cardiovascular Responses to Acute Stress
Director of Dissertation: Peggy M. Zoccola
Mindfulness includes acceptance and awareness subcomponents, and emerging theories imply that cultivating both acceptance and awareness may benefit health by diminishing stress reactivity. Yet, no prior work has manipulated awareness and acceptance simultaneously to begin to test this claim. To address this knowledge gap, 202 participants were enrolled in a 2 x 2 between-subjects experimental design manipulating both awareness (enhanced awareness v. no enhanced awareness) and acceptance
(acceptance training v. no acceptance training) of physiological responses to a cold pressor test. Cardiovascular indices were recorded throughout. The awareness manipulation and acceptance training did not independently influence cardiovascular responses, but the combination of enhanced awareness and no acceptance training condition led to higher total peripheral resistance, higher respiratory sinus arrhythmia, and lower cardiac output reactivity than the “enhanced awareness + acceptance training” and the “no enhanced awareness + no acceptance training” conditions. Blood pressure and pre-ejection period were unaffected by the acceptance training or the enhanced awareness manipulation. These results add to a growing body of work suggesting that mindful awareness and acceptance subcomponents interact to influence stress reactivity. 4
Dedication
I would like to dedicate this dissertation to my family and friends for their continued
support throughout my graduate school career.
5
Acknowledgments
I would like to thank my graduate adviser, Dr. Peggy M. Zoccola, for guiding me through the doctoral journey with patience, understanding, and wisdom. I would also like to thank my undergraduate adviser, Dr. Ian M. Handley, for introducing me to psychological research. I truly feel like I won the adviser lottery twice.
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Table of Contents
Page
Abstract ...... 3 Dedication ...... 4 Acknowledgments...... 5 List of Tables ...... 9 List of Figures ...... 10 Introduction ...... 11 Knowledge Gaps ...... 13 The Present Study ...... 14 Material and Method ...... 16 Participants ...... 16 Procedure ...... 16 Materials ...... 18 Cold pressor test...... 18 Acceptance manipulation...... 19 Awareness manipulation...... 20 Electrocardiography and impedance cardiography data collection...... 20 Measures ...... 21 Cardiovascular outcomes...... 21 Manipulation checks...... 22 Descriptive characteristics...... 24 Analytic Plan ...... 24 Missing and outlying data...... 24 Modeling cardiovascular outcomes...... 25 Test of primary hypotheses...... 25 Treatment of covariates...... 26 Results ...... 28 Evaluation of Random Assignment ...... 28 Manipulation Checks ...... 28 Tests of Temporal Effects on Cardiovascular Parameters ...... 29 Tests of Proposed Covariates on Cardiovascular Parameters ...... 30 7
Main Effect of Acceptance on Cardiovascular Parameters ...... 31 Main Effect of Awareness on Cardiovascular Parameters ...... 32 Interactive Effects of Acceptance and Awareness on Cardiovascular Parameters ..... 33 Respiratory sinus arrhythmia ...... 33 Cardiac output ...... 34 Total peripheral resistance ...... 36 Other cardiovascular measures...... 37 Discussion ...... 38 Conclusion ...... 49 References ...... 50 Tables and Figures ...... 62 Appendix A: Acceptance Training Scripts ...... 70 Acceptance Training Script - Acceptance ...... 70 Acceptance Training Script – Control ...... 72 Appendix B: Acceptance Manipulation Check Questions...... 74 Manipulation Check Questions – Acceptance ...... 74 Acceptance Use Questionnaire ...... 75 Appendix C: Random Assignment and Psychological Measures ...... 76 Measures ...... 76 Trait mindfulness...... 76 Perceived stress...... 77 Depressive symptoms...... 77 Habitual coping strategies...... 77 Optimism...... 78 Pain catastrophizing...... 78 Pain resilience...... 78 Results ...... 79 Supplemental References ...... 80 Supplemental Tables ...... 82 Appendix D: Multilevel Model Equations ...... 83 Prototypical Equations for Tests of Hypothesis 1...... 83 Prototypical Equations for Tests of Hypothesis 2...... 84 Prototypical Equations for Tests of Hypothesis 3...... 85 8
Appendix E: Supplemental Interaction Tests ...... 87 Sex x Acceptance x Awareness x Sampling Occasion ...... 87 CPT Immersion Duration x Acceptance x Awareness x Sampling Occasion ...... 88 Supplemental Figures...... 92
9
List of Tables
Page
Table 1. Characteristics of the final sample by condition...... 62
Table 2. Temporal contrasts of cardiovascular parameters...... 63
10
List of Figures
Page
Figure 1. Laboratory visit timeline...... 64
Figure 2. Temporal effects across study conditions...... 65
Figure 3. Main effect of acceptance training...... 66
Figure 4. Main effect of enhanced awareness manipulation...... 67
Figure 5. Interactive effects of awareness and acceptance conditions...... 69 11
Introduction
Stress promotes the development of numerous disorders (Lovallo, 2015), including cardiovascular disease, which remains the leading cause of death in the United
States (Kochanek, Murphy, Xu, & Arias, 2017). A major link between stressors and illness lies in the potentially damaging effects of biological stress responses (McEwen,
1998). Episodes of acute stress can activate peripheral stress response cascades like the sympathetic-adrenal-medullary axis, resulting in the release of primary stress mediators that can modify the functioning of various biological processes. For example, repeated cardiovascular activation (mediated by catecholamine release) is thought to contribute to hypertension via structural adaptation of blood vessels (i.e., vessel wall thickening;
Johsson & Hansson, 1977; Mayet, 2003). Consistent with this view, several prospective studies found that excessive blood pressure responses to acute laboratory stressors predict increased risk of future hypertension and cardiovascular mortality (e.g., Kasagi,
Akahoshi, & Shimaoka, 1995; Menkes et al., 1989; Palatini, 1998).
Given that cardiovascular stress responses predict future cardiovascular health
(Heponiemi et al., 2007; Rozanski, Blumenthal, & Kaplan, 1999; Treiber et al., 2003), researchers and clinicians have worked to develop interventions aimed at mitigating cardiovascular stress responses. Among such interventions is mindfulness, or the practice of monitoring present moment experiences with acceptance (Creswell, 2017).
Mindfulness interventions can seemingly help a broad range of individuals cope with clinical and non-clinical problems (Grossman, Niemann, Schmidt, & Walach, 2004), and current theories posit that mindfulness training is able to improve a variety of health 12 outcomes by buffering against the effects of stress on health (Creswell & Lindsay, 2014).
In particular, mindfulness may improve health by diminishing the magnitude of acute physical stress responses. Nevertheless, the extant literature provides mixed evidence for the claim that mindfulness reduces the magnitude of cardiovascular or neuroendocrine responses to acute stressors (e.g., Brown, Weinstein, & Creswell, 2012; Creswell, Pacilio,
Lindsay, & Brown, 2014; Manigault et al., 2019; Manigault, Woody, Zoccola, &
Dickerson, 2018; Nyklíček, Van Beugen, Ramakers, & Van Boxtel, 2013; Tang et al.,
2007).
Potentially contributing to these mixed results, limited work distinguishes between sub-components of mindfulness. Yet, mindfulness is hypothesized to involve two primary sub-components: awareness and acceptance (Bishop et al., 2006; Lindsay &
Creswell, 2017). Awareness refers to the use of attention to monitor one’s present- moment experiences whereas acceptance is a mental attitude of nonjudgment toward those experiences (Bishop et al., 2006). Moreover, awareness and acceptance may not contribute equally to the stress buffering effect of mindfulness. Some prior work implies that awareness and acceptance independently influence stress-related outcomes. For example, greater acceptance is associated with decreased evening cortisol (Manigault et al., 2017), and decreased cardiovascular responses to emotional stimuli (Dan-Glauser &
Gross, 2015). In contrast, greater self-reported awareness has been found to increase sensitivity to fear and anxiety provoking thoughts (Hamill, Pickett, Amsbaugh, & Aho,
2015). To explain how awareness and acceptance are able to produce these effects,
Monitor and Acceptance Theory (Lindsay & Creswell, 2017) states that acceptance 13 reduces reactivity to negatively valanced stimuli whereas awareness heightens the experience of both positive and negative stimuli, and thus can render the perception of distressing events more intense. Moreover, Monitor and Acceptance Theory predicts that mindful awareness and acceptance interact such that high awareness and low acceptance will heighten affective reactivity whereas high awareness and high acceptance will reduce affective reactivity, thereby diminishing stress responses and improving stress- related health outcomes. Supporting Monitor and Acceptance Theory, a recent study found that a 14-day mindfulness intervention aimed at cultivating both mindful awareness and acceptance was associated with decreased systolic blood pressure and cortisol reactivity to an acute social-evaluative stressor relative to training aimed at cultivating only mindful awareness, or an active control condition (Lindsay, Young,
Smyth, Brown, & Creswell, 2018). In sum, a growing literature suggests that mindful awareness and acceptance do not promote stress buffering to the same extent, and
Monitor and Acceptance Theory implies that the combination of mindful awareness and acceptance drive the stress buffering effects of mindfulness at least partially by diminishing physiological stress responses.
Knowledge Gaps
However, only one study to date experimentally tested predictions of Monitor and
Acceptance Theory, thus warranting replication. Moreover, no prior study has simultaneously manipulated both awareness and acceptance to test predictions of MAT;
Lindsay et al., (2018) contrasted awareness + acceptance with awareness-only training.
Yet, other combinations of acceptance and awareness are meaningful. For example, no 14 prior work has tested if training in acceptance-only would produce effects comparable to the combination of awareness and acceptance. Accordingly, the present study aimed to replicate and extend prior work testing predictions of Monitor and Acceptance Theory by simultaneously manipulating mindful awareness and acceptance.
The Present Study
The present study used a 2 x 2 between-subject experimental design manipulating both acceptance (acceptance training versus no acceptance training) and awareness
(enhanced awareness versus no enhanced awareness) to compare all possible combinations of awareness and acceptance. Departing from past literature, the present study manipulated domain-specific forms of awareness and acceptance, such that the awareness manipulation and acceptance training specifically targeted participant’s physiological responses to a cold pressor test. Mindful awareness and acceptance subcomponents are broadly defined in terms of “present moment experiences.” As a result, traditional mindfulness training is lengthy because it requires that participant practice mindful awareness and acceptance in varied contexts. Yet, for the purposes of the present study, participants only needed to be mindfully aware and/or accepting during the stressor task. Accordingly, the present manipulations specifically targeted participant’s physiological responses to the cold pressor test.
Finally, to examine interrelated components of the cardiovascular response, primary outcomes of the study included: systolic blood pressure (SBP), diastolic blood pressure (DBP), respiratory sinus arrhythmia (RSA), pre-ejection period (PEP), cardiac output (CO), and total peripheral resistance (TPR). These outcomes yield complementary 15 information. For example, the joint modulation of CO and TPR produces blood pressure responses (Andreassi, 2013), and the heart is subject to sympathetic and parasympathetic control that are indexed by PEP and RSA, respectively (Stern, Ray, & Quigley, 2001). In sum, the present study included varied cardiovascular indices to produce a more nuanced and comprehensive analysis of cardiovascular stress reactivity.
To examine the independent effects of awareness and acceptance on cardiovascular stress responses, the following hypotheses were tested: (1) Participants assigned to the acceptance training were expected to display lower cardiovascular reactivity to acute stress (i.e., a lower increase in SBP, DBP, CO, and TPR from pre- stressor resting states [i.e., from baseline] to the stress task, and a lower decrease in RSA and PEP from baseline to the stress task) relative to participants in the no acceptance training condition. (2) Participants assigned to the enhanced awareness condition were expected to display greater cardiovascular reactivity to acute stress relative to participants in the no enhanced awareness condition.
To examine the interactive effect of awareness and acceptance on cardiovascular stress responses, the following hypothesis was tested: (3) Consistent with predictions of
Monitor and Acceptance Theory, we expected the effect of the awareness manipulation on cardiovascular responses to be moderated by acceptance training such that, the combination of enhanced awareness + acceptance training would lead to lower cardiovascular reactivity than the combination of enhanced awareness + no acceptance training.
16
Material and Method
Participants
A total of 202 participants were recruited from the Ohio University Psychology
Department subject pool (via SONA Systems). Participants were asked to refrain from physical exercise or consumption of caffeine and tobacco during the 2 hours preceding the start of the study visit. See Table 1 for socio-demographics characteristics of the full sample. Participants were ineligible if they reported: 1) prior mindfulness training (e.g., participation in a mindfulness-based stress reduction program), 2) used of a cardiac pacemaker, 3) used of medication with cardiac side effects, 4) if they were found to be hypertensive during the first blood pressure measurement of the study, 5) or if they reported previous injuries resulting from exposure to cold temperatures. Participants were considered hypertensive if they displayed an average systolic blood pressure above 140 mmHg, or an average diastolic blood pressure above 90 mmHg (Whitworth & World
Health Organization, International Society of Hypertension Writing Group, 2003). These exclusion criteria were used to minimize the impact of factors that may affect cardiovascular functioning or reactivity to the cold pressor test. A total of 3 participants were assessed for eligibility but not recruited into the study due to prior mindfulness training (N = 1) and high blood pressure (N = 2).
Procedure
A timeline of study procedures is presented in Figure 1. Participants were brought into the laboratory where a research assistant verbally confirmed eligibility criteria, and measured blood pressure to confirm that participants were normotensive (the BP cuff was 17 always placed on participant’s left arm). Upon confirming eligibility, participants were consented and electrodes were placed on participants to measure electrocardiography
(ECG) and impedance cardiography (ICG) throughout the study. Once research assistants confirmed that ECG and ICG data were being collected appropriately, participants were asked to remain seated for the rest of the experiment. Participants then completed questionnaires (including trait mindfulness, depressive symptoms, habitual coping strategies, pain catastrophizing, pain tolerance, and optimism) and rested for 10 minutes.
This rest period was used to allow participant to acclimate to the laboratory setting and the recording equipment. Next, half of the participants were presented with a set of pre- recorded instructions aimed at fostering acceptance of physiological stress reactions. The other half of participants completed a control task where they were presented with neutral information about typical stress responses. Following the acceptance versus no acceptance (control) training, participants completed the cold pressor test (Hines, 1932), where participants were asked to submerge their hand in cold water (0 – 4 °C) for up to 2 minutes. During the cold pressor test, participants either underwent the enhanced awareness of physiological stress reaction or no enhanced awareness manipulation. More specifically, participants in the enhanced awareness condition were shown a tablet displaying the current time of day as well as the current temperature of their hand and were instructed to monitor this display continuously. In contrast, participants in the no enhanced awareness condition were shown a tablet displaying only the current time of day (and instructed to monitor this display continuously). Following the cold pressor test, participants rested for 5 minutes. Next, participants completed post-task questionnaires 18 assessing 1) acceptance, 2) prior experience with mindfulness, and 3) health behaviors
(e.g., exercise). Upon completing these questionnaires, electrodes were removed from participants. Finally, participants were thanked for their participation, debriefed, and compensated with research credits via SONA. Randomization to study conditions was stratified by sex to achieve equivalence between conditions (i.e., separate randomization lists were used for women and men). As shown on Figure 1, electrocardiography (ECG) and impedance cardiography (ICG) were recorded continuously following electrode setup. In contrast, blood pressure was collected periodically during: 1) the consent and eligibility check, 2) the pre-task rest, 3) the pre-task (acceptance) manipulation, 4) the cold pressor test, 5) the post-task rest, and 6) the post-task surveys. Participants were compensated with course credit. The Ohio University Institutional Review Board pre- approved all procedures.
Materials
Cold pressor test. The present study used a modified version of the Cold Pressor
Test (CPT; Schwabe, Haddad, & Schachinger, 2008). The classic cold pressor test entails that participants submerge one of their hands (up to and including the wrist) in cold water
(0 – 4 °C) for up to 3 minutes. Participants were instructed to keep their right hand in a recirculating water chiller (Model II-BX Chiller, The Wine Well Chiller Company,
Milford, Conn.) for as long as they can and were told that they can remove their hand at their discretion. Participants who kept their hand submerged for 2 minutes were asked to remove it from the cold water at the 2-minute mark, consistent with prior work (e.g.,
Geers, Wellman, Helfer, Fowler, & France, 2008). Physiological stress responses to the 19 cold pressor test may be enhanced by the addition of a social-evaluative component
(Schwabe et al., 2008). As such, all participants were videotaped during the cold pressor test, and participants were instructed that video recordings would be analyzed by a panel of trained raters for facial expressions and non-verbal behaviors. This stressor task was chosen because it reliably leads to increased autonomic arousal (Schwabe & Schächinger,
2018) and may be more generalizable to other contexts than a purely physical stressor.
Acceptance manipulation. To manipulate an attitude of acceptance towards momentary physiological responses, participants were taught the Chinese finger trap analogy (Hayes, Strosahl, & Wilson, 1999). Participants were given a Chinese finger trap, and the Chinese finger trap analogy was presented verbally as on-screen text, and in the form of pre-recorded audio. In contrasts, participants in the control condition were not given a Chinese finger trap and were presented with emotionally neutral information regarding typical physiological stress responses in the form of on-screen text and pre- recorded audio. A transcript of the information presented to participants may be found in
Appendix A. This manipulation was chosen because it was previously shown to increase pain tolerance, reduce distress and diminish avoidance in the context of painful stimuli
(Branstetter-Rost, Cushing, & Douleh, 2009; Kohl, Rief, & Glombiewski, 2012; Masedo
& Rosa Esteve, 2007). In addition, this manipulation was chosen for its ability to be highly standardized through scripted recordings (unlike other manipulations that require the help of experimenters; e.g., Roche, Forsyth, & Maher, 2007). Finally, this manipulation was chosen because it is relatively brief (existing acceptance manipulations vary from 2 minutes to 20 minutes; e.g., Branstetter-Rost et al., 2009; Vowles et al., 20
2007) and thus would better match the duration of the acceptance manipulation. This is important because the present study aimed to examine the independent effects of awareness and acceptance manipulations, and using manipulations of comparable duration is necessary to validly compare their independent effects.
Awareness manipulation. To manipulate awareness, a tablet was placed in front of participants during the cold pressor test. Among participants assigned to the enhanced awareness condition, the tablet displayed the current time of day and the temperature of their (submerged) hand during the task. This was achieved by placing a sensor on participant’s right wrist and instructing them that this sensor will monitor the temperature of their hand during the task. In fact, the temperature feedback presented to participants was pre-programmed in the tablet (displaying a decelerating decrease in temperature starting at 98.6°F and ending between 42.0°F and 42.9°F; reaching 62°F at the 30 second mark and 48°F at the 60 second mark). This precaution was used to eliminate between- subject variability in temperature feedback. In contrast, participants in the non-awareness condition were only shown the current time of day and no sensor was placed on their wrist. All participants were asked to look directly at the tablet during the entire task.
Electrocardiography and impedance cardiography data collection. Three disposable Ag/AgCl spot electrodes were placed on participants in a lead-2 configuration to measure ECG. The ECG signal was acquired at 1000 Hz using the MP150 (Biopac
Systems Inc., Goleta, CA) and a single ECG amplifier module (ECG100C). In addition, 4 aluminum band electrodes were placed on participants to measure ICG. Two band electrodes were placed at the base of participants’ necks, and two band electrodes were 21 placed on subject’s torso, below the xiphoid complex of the sternum. Impedance magnitude (Z0) and its derivative (dZ/dt) were acquired at 1000 Hz using the MP150
(Biopac Systems Inc., Goleta, CA) and a two channel ICG amplifier module
(NICO100C).
Measures
Cardiovascular outcomes. Co-primary outcomes of the study included SBP,
DBP, RSA, PEP, CO, and TPR. The OMRON® digital blood pressure monitor (Model:
HEM-907XL) was used to measure SBP and DBP during the consent and eligibility check, the pre-task rest, the pre-task (acceptance v. non-acceptance) manipulation, the cold pressor test, the post-task rest, and the post-task surveys. Raw ECG data was processed in 1-minute segments on HRV 3.2.4 (MindWare Technologies LTD) to estimate RSA power (ln[ms]2). ECG data were visually inspected for artifacts, and incorrectly identified peaks were corrected. One-minute segments where more than 25% of peaks were miss-identified were treated as missing data. IMP 3.2.3 (MindWare
Technologies LTD) was used to process 1-minute segment of ECG and ICG data and derive PEP (ms) and CO (L/min). Stroke volume was computed using the Bernstein-
Lemmens methods (Bernstein & Lemmens, 2005). Once again, ECG/ICG data were visually inspected for artifacts and/or incorrect placement of B/Z/X points, and corrected.
Segments where more than 25% of data were considered artifacts were treated as missing data (6.72% of all raw ECG and ICG segments were excluded on this basis). Consistent with prior work (Sherwood et al., 1990), TPR (dynes⋅sec⋅cm-5) was computed as (((SBP 22
+ 2 * DBP) / 3) / CO) * 80. Raw ECG an ICG data were re-processed as 30-second
(instead of 1-minute) segments for the CPT portion of the study.
Each 1-minute segment were averaged over their respective study portion to derive average RSA, PEP, CO, and TPR estimates for 1) the pre-task rest, 2) the pre-task manipulation, 3) the post-task rest, and 4) the post-task surveys. For the CPT, 30-second segments were averaged over the full length of the CPT. Given that participants varied in how long they kept their hand submerged in cold water, the number of 30-second segments used to derive average estimates of RSA, PEP, CO, and TPR during the CPT also varied (i.e., one 30-second segment for CPTs lasting less than 45 seconds; two 30- second segments for CPTs lasting between 46 and 75 seconds; three 30-second segments for CPTs lasting between 76 and 105 seconds; four 30-second segments for CPTs lasting more than 106 seconds).
Manipulation checks. Manipulation checks of the present study examined: 1) the degree to which the acceptance manipulation was understood by participants and led to increased self-reported acceptance, 2) the degree to which participants were attentive to the awareness manipulation, and 3) the degree to which the stressor task elicited pain.
Participants assigned to the acceptance condition were quizzed about their acceptance using 3 items following the manipulation and given feedback (i.e., told the correct answer to quiz items). An example item is “During the upcoming tasks I should try to…”, and is answered correctly by selecting “Be accepting of my physiological reactions.” In addition, as part of post-task questionnaires, all participants were asked to report the degree to which they remained accepting of their experiences during the CPT 23 and subsequent rest period on a 5-point scale (1 = not at all; 5 = very much), with greater scores reflecting greater acceptance. Self-reported acceptance scores during and after the
CPT were analyzed separately. Acceptance training manipulation checks are available in
Appendix B.
To check if participants were looking at the tablet (as part of the enhanced awareness manipulation), a trained research assistant blind to study conditions reviewed video recordings of the cold pressor test to code for the total duration of time looking away from the tablet. To account for varying duration of the cold pressor test, a % tablet awareness score was computed, where % tablet awareness = (total time spent looking at the tablet)/ (total duration of hand immersion)*100. Greater % tablet awareness scores reflect greater engagement with the enhanced awareness manipulation.
The success of the CPT was evaluated with respect to three pain outcomes: pain threshold, pain tolerance, and pain ratings. Pain threshold was measured by asking participants to verbally state when they first felt pain during the CPT. Pain threshold was recorded as the time (in seconds) elapsed between the start of the CPT and participants stating that they feel pain. Pain tolerance was operationalized as the total amount of time
(in seconds) during which the participant’s hand remained submerge in cold water during the CPT. Consistent with prior work (Bird & Dickson, 2001), subjective pain was measured using a 10 cm visual analog scale anchored by the words “No Pain” and “Pain as bad as it could possibly be”. Participants drew a mark on the scale to report pain rating. Subsequently, pain ratings were coded on a scale from 0 to 100 based on the distance (in millimeters) between the left edge of the scale (i.e., no pain) and the spot 24 marked by participants. Pain ratings were obtained immediately after the participant removed their hand from the cold water. Consistent with prior work (e.g., Branstetter-
Rost et al., 2009), pain threshold, pain tolerance, and pain ratings were analyzed separately.
Descriptive characteristics. Participants completed supplemental self-reported measures to describe characteristics to the student sample and evaluate the success of random assignment. Participants were instructed to provide sociodemographic information including age, biological sex at birth, education, and racial/ethnic background. Participants were also asked to report any prior experience with mindfulness as well as recent health behaviors including consumption of tobacco, caffeine, alcohol, and physical activity. The present study also included measures of trait mindfulness, depressive symptoms, habitual coping strategies, optimism, pain catastrophizing, and pain resilience. See Appendix C for a description of these scales and a result section examining equivalence between study conditions.
Analytic Plan
Missing and outlying data. Primary outcomes of interest (i.e., SBP, DBP, RSA,
PEP, CO, TPR) were all measured on 5 occasions (i.e., the pre-task rest, pre-task manipulation, cold pressor test, post-task rest, and post-task survey), for a total of 1,010 possible data points. In total, 20 measurements were missing for PEP (2.0%), and 23 measurements were missing for RSA, CO and TPR (2.3%). In addition, 10 SBP, 12 DBP,
3 RSA, 9 PEP, 12 CO and 15 TPR values were considered outliers (i.e., more than 3 SDs 25 from the mean). To assess the effect of these outlying values, all tests of primary hypotheses are reported while including and excluding outlying values.
Modeling cardiovascular outcomes. Maximum likelihood mixed linear models were used to examine the effect of sampling occasions (i.e., pre-task rest, pre-task manipulation, CPT, post-task rest, post-task surveys), and study conditions (i.e., the acceptance training and awareness manipulation) on primary outcomes of interest (i.e.,
SBP, DBP, RSA, PEP, CO, TPR) using SAS 9.4/STAT 13.1 (SAS Institute Inc., Cary,
N.C). Two-level models were used where sampling occasions (level-1) were nested within individuals (level-2). The level-1 fixed effect of sampling occasion was dummy coded to contrast pre-stressor resting levels with all other sampling occasions (i.e., the resulting dummy coded variables all referenced pre-task resting levels). The effects of the acceptance training and the enhanced awareness manipulation were also dummy coded (0
= no acceptance training, 1 = acceptance training; 0 = no enhanced awareness, 1 = enhanced awareness) and entered as level-2 fixed effects. In all models, level-2 intercepts were modeled as random effects using an identity matrix.
Test of primary hypotheses. To test Hypothesis 1, the dummy coded effect of acceptance training was entered as a level-2 fixed effect and allowed to interact with all level 1 fixed effects. To test Hypothesis 2, the dummy coded effect of the enhanced awareness manipulation was entered as a level 2 fixed effect and allowed to interact with all level-1 fixed effects. For Hypothesis 3, fixed effects of the acceptance training and the enhanced awareness manipulation were allowed to interact with each other as well as all level-1 fixed effects. See Appendix D for model equations. Given that the present 26 hypotheses pertained to reactivity (or a change from a resting state), follow-up contrasts for tests of primary hypotheses consistently referenced pre-stressor resting levels such that the pre-task manipulation, CPT, post-task rest, and post-task questionnaires were compared to a “baseline” pre-stressor resting state. While primary hypotheses would be fully captured by contrasts of pre-stressor resting levels and the CPT, other contrasts referencing pre-stressor resting levels were included to more fully capture temporal changes in cardiovascular outcomes, and determine if the effect of the acceptance training and the enhanced awareness manipulation were unique to CPT-reactivity (as opposed to reactivity to the acceptance training task, or recovery following the CPT).
Treatment of covariates. Prior work implies that sex, BMI, caffeine, tobacco, and exercise are associated with cardiovascular functioning (Carroll, Phillips, & Der,
2008; Crews & Landers, 1987; Hastrup & Light, 1984; Lane & Williams, 1985;
Sheffield, Smith, Carroll, Shipley, & Marmot, 1997). Similarly, individuals who kept their hand submerged for longer were exposed to the stressor/enhanced awareness manipulation for a longer duration, and thus may exhibit greater cardiovascular responses. As such, biological sex, BMI, CPT immersion duration, as well as caffeine, tobacco and alcohol consumption were considered as potential covariates. The effect of these variables was tested on each primary outcome of interest (i.e., SBP, DBP, RSA,
PEP, CO, TPR) in separate 2-level models where each covariate was allowed to interact with all level 1 fixed effects. Covariates found to predict intercepts or interact with sampling occasion for at least one primary outcome were retained. Tests of primary hypotheses are reported while including/excluding covariates. Follow-up contrasts of 27 significant interactions were conducted on models which included mean-centered covariates (with the exception of gender which was centered on males) and excluded outlying values.
Prior research implies that men and women may respond differently to mindfulness training (e.g., Chen, Comerford, Shinnick, & Ziedonis, 2010; Rojiani,
Santoyo, Rahrig, Roth, & Britton, 2017). In addition, the effect of the acceptance training and the enhanced awareness manipulation may be stronger for individuals who kept their hand submerged for longer. As such, sex and CPT immersion duration were also considered as potential moderators of the effects of awareness and acceptance on primary outcomes. Tests of 4-way interactions of sex x awareness x acceptance x sampling occasion and CPT immersion duration x awareness x acceptance x sampling occasion are reported in Appendix E.
28
Results
Evaluation of Random Assignment
As shown on Table 1 and Supplemental Table S-1 (Appendix C) participants assigned to each study conditions did not differ on the basis of sex, race, ethnicity, education, age, caffeine/tobacco/alcohol consumption, physical activity, yoga practice, pre-task resting levels of SBP, DBP, RSA, PEP, CO, TPR, trait mindfulness, perceived stress, depressive symptoms, habitual coping strategies, optimism, pain catastrophizing, or pain resilience (all ps >.05).
Manipulation Checks
Suggesting that participants understood the Chinese finger trap analogy, 88 of 101
(87.1%) participants assigned to the acceptance training condition correctly answered all three post-manipulation questions. Furthermore, participants assigned to the acceptance training reported that they remained marginally more accepting of their experiences during the CPT (t(200) = 1.68, p = .094, d = .24) and significantly more accepting during the post-task rest (t(200) = 2.25, p = .025, d = .32) than participants assigned to the no acceptance training condition.
On average, participants spent 86.36% of the total time during which their hand was submerged in cold water looking at the tablet, and this percentage did not differ between the enhanced awareness (M = 85.67; SD = 17.80) and no enhanced awareness
(M = 87.06; SD = 17.90) conditions (t(199) = 0.55, p = .58, d = .07), suggesting that the enhanced awareness and no enhanced awareness conditions were equally and highly engaging. 29
The CPT successfully elicited pain in participants (pain threshold: M = 25.8, SD =
19.4; pain tolerance: M = 63.7, SD = 40.5; pain ratings: M = 66.8, SD = 18.6). However, pain threshold, pain tolerance, and subjective pain ratings did not differ by condition (i.e., acceptance, awareness, or the interaction of acceptance by awareness did not significantly predict pain outcomes; all ps > .05). Moreover, while males (M = 74.66; SD = 44.33) displayed greater pain tolerance than females (M = 57.58; SD = 37.07; t(199) = 2.91, p =
.004, d = .41), sex did not predict pain threshold and pain ratings, or interact with awareness, acceptance or awareness x acceptance to predict pain tolerance, pain threshold or pain ratings (all ps > .05).
Tests of Temporal Effects on Cardiovascular Parameters
Cardiovascular reactivity was first examined across study conditions to provide a frame of reference for tests of primary hypotheses. Sampling occasion predicted SBP
(F(4, 804) = 129.64, p < .001), DBP (F(4, 804) = 122.62, p < .001), RSA (F(4, 781) =
31.03, p < .001), PEP (F(4, 787) = 3.60, p = .006), CO (F(4, 784) = 52.07, p < .001), and
TPR (F(4, 784) = 17.92, p < .001). Follow-up pairwise contrasts for all sampling occasions are presented in Table 2. As shown in Figure 2, SBP, DBP, TPR, and CO all significantly increased from the pre-task rest to the CPT, and RSA significantly decreased from the pre-task rest to the CPT, suggesting that the CPT successfully elicited cardiovascular responses. However, PEP levels only marginally decreased from the pre- task rest to the CPT (p = .07). 30
Tests of Proposed Covariates on Cardiovascular Parameters
Across all sampling occasions, sex predicted SBP (F(1,808) = 48.41, p < .001),
DBP (F(1,808) = 8.58, p = .003), PEP (F(1,791) = 7.48, p =.006), CO (F(1,788) = 88.08, p <.001), and TPR (F(1,788) = 63.51, p <.001), such that females displayed lower SBP,
PEP, CO than males, as well as higher DBP and TPR than males. Sex also interacted with sampling occasion to predict CO (F(4,780) = 5.43, p < .001) and TPR (F(4,780) = 2.63, p
= .033) reactivity. Relative to males, females displayed significantly lower increases in
CO (b = -0.16, t(1,780) = 2.97, p = .003, 95% CI [-0.27, -0.05]) and larger increases in
TPR (b = 112.25, t(1,780) = 2.82, p = .005, 95% CI [34.01, 190.49]) from the pre-task rest to the CPT.
Across sampling occasions, BMI predicted SBP (F(1,808) = 11.17, p < .001),
DBP (F(1,808) = 18.56, p < .001), CO (F(1,788) = 68.14, p <.001), and TPR (F(1,788) =
43.62, p <.001), such that greater BMI was associated with higher SBP, DBP, CO and lower TPR. There was no association between BMI and cardiovascular reactivity.
Duration of CPT hand immersion interacted with sampling occasion to predict
SBP (F(4,796) = 3.38, p = .009) and CO (F(4,776) = 4.42, p = .001) reactivity, such that individuals who submerged their hands in the cold water for longer durations showed a larger increases in SBP and CO from the pre-task rest to the CPT (b = 0.041, t(1,796) =
2.37, p = .017, 95% CI [0.007, 0.075], and b = 0.002, t(1,776) = 4.01, p < .001, 95% CI
[0.001, 0.003], respectively).
Caffeine use interacted with sampling occasion to predict RSA reactivity
(F(4,773) = 5.79, p < .001), such that greater consumption of caffeinated beverages on 31 the day of the study was associated with larger decreases in RSA from the pre-task rest to the CPT (b = -0.28, t(1,773) = 4.43, p < .001, 95% CI [-0.40, -0.15]). Similarly, tobacco use interacted with sampling occasion to predict SBP (F(4,796) = 2.81, p = .024), such that greater tobacco consumption on the day of the experiment was associated with larger increases in SBP from the pre-task rest to the CPT (b = 14.47, t(1,796) = 2.91, p = .003,
95% CI [4.70, 24.24]). Alcohol use predicted SBP (F(1,800) = 7.31, p = .007) and CO
(F(1,780) = 8.70, p = .003) across sampling occasion, such that greater alcohol consumption on the day of the experiment was associated with greater SBP and CO across all sampling occasion.
Given the associations between cardiovascular indices and sex, BMI, CPT immersion duration, as well as caffeine, tobacco, and alcohol consumption, all proposed variables were retained as covariates in final analyses.
Main Effect of Acceptance on Cardiovascular Parameters
To test the hypothesis that the acceptance training would decrease cardiovascular reactivity to the CPT (Hypothesis 1) relative to a no acceptance (control) training, the acceptance condition x sampling occasion interactions were examined. Assignment to the acceptance condition interacted with sampling occasion to predict PEP (F(4,738) = 2.72, p = .03). However, contrary to Hypothesis 1, this interaction was driven by the pre-task manipulation, where participants assigned to the acceptance training showed a less negative decrease in PEP from pre-task rest to the pre-task manipulation relative to participants assigned to the no acceptance training condition (b = 4.39, t(1,738) = 2.77, p
= .005, 95% CI [1.27, 7.50]). No other contrasts referencing the pre-task rest period were 32 significant (all ps > .51). Moreover, the interaction of the acceptance condition by sampling occasion was non-significant when predicting SBP (F(4,754) = 0.86, p = .48),
DBP (F(4,753) = 0.68, p = .60), RSA (F(4,738) = 0.35, p = .84), CO (F(4,734) = 1.79, p
= .13), and TPR (F(4,731) = .96, p = .42). Removing covariates from the model and/or reintroducing outlying values did not alter these findings. Furthermore, assignment to the acceptance condition did not predict levels of SBP, DBP, RSA, PEP, CO, or TPR across sampling occasions (all ps > .05). In summary, contrary to Hypothesis 1, assignment to the acceptance training condition did not moderate the pre-task rest to CPT change in
SBP, DBP, RSA, PEP, CO, or TPR. See Figure 3 for a graphical representation of these interactions.
Main Effect of Awareness on Cardiovascular Parameters
To test the hypothesis that the awareness manipulation would increase cardiovascular reactivity to the CPT (Hypothesis 2), interactions of awareness condition by sampling occasion were examined. The interaction of awareness condition by sampling occasion was non-significant when predicting SBP (F(4,753) = 1.08, p = .36),
DBP (F(4,754) = 0.76, p = .55), RSA (F(4,738) = 0.64, p = .63), PEP (F(4,738) = 0.32, p
= .86), CO (F(4,734) = 1.43, p = .22), and TPR (F(4,731) = 1.55, p = .18). Removing covariates from the model and/or reintroducing outlying values did not alter these findings. Across sampling occasion, assignment to the enhanced awareness condition significantly predicted PEP (F(1,738) = 4.15, p = .042) and marginally predicted TPR
(F(1,731) = 3.50, p = .061), such that participants assigned to the enhanced awareness condition displayed lower PEP and TPR than participants assigned to the no enhanced 33 awareness condition. Furthermore, assignment to the awareness condition did not predict levels of SBP, DBP, RSA, or CO across sampling occasion (all ps > .05). In summary, contrary to Hypothesis 2, assignment to the enhanced awareness manipulation did not moderate the pre-task rest to CPT change in SBP, DBP, RSA, PEP, CO, or TPR. See
Figure 4 for a graphical representation of these interactions.
Interactive Effects of Acceptance and Awareness on Cardiovascular Parameters
To test the hypothesis that the effect of the enhanced awareness manipulation on cardiovascular responses to be moderated by the acceptance training (Hypothesis 3), the awareness condition x acceptance condition x sampling occasion interactions were examined.
Respiratory sinus arrhythmia. The acceptance x awareness x sampling occasion interaction was significant when predicting RSA (F(4,730) = 3.19, p = .013), and remained significant when excluding covariates from the model (F(4,766) = 2.97, p =
.019), reintroducing outlying values (F(4,733) = 3.42, p = .008), or both excluding covariates and including outliers (F(4,769) = 3.19, p = .013). The acceptance by awareness interaction significantly predicted the change from pre-task resting levels of
RSA to the CPT (b = 0.51, t(1,730) = 2.54, p = .011, 95% CI [0.11, 0.91]) but not the change from pre-task resting levels to the pre-task manipulation, post-task rest, or post- task surveys (all ps > .05). Consistent with Figure 5 (panels c1 and c2), among individuals assigned to the enhanced awareness condition, the acceptance training condition led to smaller decreases in RSA than the no acceptance training condition (b =
0.34, t(1,730) = 2.41, p = .016, 95% CI [0.06, 0.62]). In contrast, assignment to the 34 acceptance training condition did not predict the magnitude of the decrease in RSA from the pre-task rest to the CPT among individuals assigned to the no enhanced awareness condition (b = -0.16, t(1,730) = 1.17, p = .24, 95% CI [-0.45, 0.11]). Additional between- group contrasts of the pre-task rest to CPT change in RSA revealed that participants assigned to the “no acceptance training + enhanced awareness” aware condition also displayed significantly larger decreases in RSA than participants assigned to the “no acceptance training + no enhanced awareness” condition (b = 0.37, t(1,730) = 2.54, p =
.011, 95% CI [0.08, 0.65]); no other contrasts were significant (all ps > .05). In addition, all groups displayed marginal or significant decreases in RSA from the pre-task rest to the CPT (acceptance training + enhanced awareness: b = -0.26, t(1,730) = 2.13, p = .033,
95% CI -0.50, -0.01]; no acceptance training + enhanced awareness: b = -0.60, t(1,730) =
4.89, p < .001, 95% CI [-0.84, -0.36]; acceptance training + no enhanced awareness: b = -
0.40, t(1,730) = 3.37, p < .001, 95% CI [-0.63, -0.16]; no acceptance training + no enhanced awareness: b = -0.23, t(1,730) = 1.89, p = .059, 95% CI [-0.47, 0.01]).
Cardiac output. The acceptance x awareness x sampling occasion interaction was significant when predicting CO (F(4,726) = 5.58, p < .001), and remained significant when excluding covariates from the model (F(4,762) = 3.63, p = .006), or reintroducing outlying values (F(4,733) = 3.42, p = .008), but was non-significant when both excluding covariates and including outliers (F(4,792) = 1.71, p = .14). The acceptance by awareness interaction significantly predicted the change from pre-task resting levels of CO to the
CPT (b = 0.41, t(1,726) = 4.21, p < .001, 95% CI [0.21, 0.60]) but not the change from pre-task resting levels to the pre-task manipulation, post-task rest, or post-task surveys 35
(all ps > .05). Consistent with Figure 5 (panels e1 and e2), among individuals assigned to the enhanced awareness manipulation, the acceptance training led to significantly larger increases in CO from the pre-task rest to the CPT than the no acceptance training condition (b = 0.31, t(1,726) = 4.58, p < .001, 95% CI [0.18, 0.45]). In contrast, for participants assigned to the no enhanced awareness condition, assignment to the acceptance training did not predict pre-task rest to CPT changes in CO (b = -0.09, t(1,726) = 1.37, p = .17, 95% CI [-0.23, 0.04]). Additional between-group contrasts of the pre-task rest to CPT change in CO revealed that participants assigned to the “acceptance training + enhanced awareness” condition also displayed significantly larger increases in
CO than participants assigned to “acceptance training + no enhanced awareness” condition (b = 0.19, t(1,730) = 2.85, p = .004, 95% CI [0.06, 0.33]). Furthermore, participants assigned to the “no acceptance training + no enhanced awareness” condition displayed significantly larger increases in CO than participants assigned to “no acceptance training + enhanced awareness” condition (b = 0.21, t(1,730) = 3.08, p = .002,
95% CI [0.07, 0.34]); no other contrasts were significant (all ps > .05). Yet, all groups displayed a significant increase in CO from the pre-task rest to the CPT (acceptance training + enhanced awareness: b = 0.45, t(1,726) = 7.42, p < .001, 95% CI [0.33, 0.56]; no acceptance training + enhanced awareness: b = 0.13, t(1,726) = 2.24, p = .025, 95% CI
[0.01, 0.25]; acceptance training + no enhanced awareness: b = 0.25, t(1,726) = 4.27, p <
.001, 95% CI [0.13, 0.36]; no acceptance training + no enhanced awareness: b = 0.34, t(1,726) = 5.87, p < .001, 95% CI [0.23, 0.46]). 36
Total peripheral resistance. The acceptance x awareness x sampling occasion interaction was significant when predicting TPR (F(4,723) = 2.92, p = .020), and remained marginally significant when removing covariates from the model (F(4,758) =
2.31, p = .056). However, this interaction was non-significant when outliers were reintroduced (F(4,736) = 1.65, p = .15) or when both covariates were excluded and outliers were included (F(4,772) = 0.87, p = .48). The acceptance by awareness interaction significantly predicted the change from pre-task resting levels of TPR to the
CPT (b = -188.24, t(1,726) = 2.81, p = .005, 95% CI [0.-319.62, -56.85]) but not the change from pre-task resting levels to the pre-task manipulation, post-task rest, or post- task surveys (all ps > .05). Consistent with Figure 5 (panels f1 and f2), among those assigned to the enhanced awareness condition, participants assigned to the no acceptance training condition displayed greater increases in TPR from the pre-task rest to the CPT than participants assigned to the acceptance training condition (b = 125.20, t(1,723) =
2.66, p = .008, 95% CI [32.77, 217.63]). In contrast, when participants were assigned to the no enhanced awareness condition, assignment to the acceptance training condition was unrelated to the magnitude of the change in TPR from the pre-task rest to the CPT (b
= 63.03, t(1,723) = 1.31, p = .18, 95% CI [-31.12, 157.20]). Driving this interaction, participants in the “acceptance training + enhanced awareness” group showed no significant increase in TPR from the pre-task rest to the CPT (b = 14.12, t(1,723) = 0.34, p = .73, 95% CI [-66.48, 94.72]) whereas participants assigned to the “no acceptance training + enhanced awareness” group showed a significant increase in TPR from the pre- task rest to the CPT (b = 139.32, t(1,723) = 3.44, p < .001, 95% CI [59.81, 218.83]). In 37 contrast, participants in the “acceptance training + no enhanced awareness” only showed a marginal increased from the pre-task rest to the CPT (b = 73.67, t(1,723) = 1.84, p =
.066, 95% CI [-5.11, 152.46]) while participants in the “no acceptance training + no enhanced awareness” condition showed a non-significant increased from the pre-task rest to the CPT (b = 10.63, t(1,723) = 0.26, p = .79, 95% CI [-69.24, 90.51]). Consistent with these results, additional between-group contrasts of the pre-task rest to CPT change in
TPR revealed that participants assigned to the “no acceptance training + enhanced awareness” condition also displayed significantly larger increases in TPR than participants assigned to “no acceptance training + no enhanced awareness” condition (b =
128.69, t(1,730) = 2.69, p = .007, 95% CI [34.61, 222.75]); no other contrasts were significant (all ps > .05).
Other cardiovascular measures. The acceptance x awareness x sampling occasion interaction was non-significant when predicting SBP (F(4,746) = 0.23, p = .92),
DBP (F(4,746) = 0.45, p = .77), and PEP (F(4,730) = 0.29, p = .88). Removing covariates from the model and/or reintroducing outlying values did not alter these findings. A graphical representation of the acceptance x awareness x sampling occasion interaction predicting SBP, DBP and PEP is presented in Figure 5 (panels a, b, and d).
38
Discussion
The present study tested the independent and interactive effects of a brief acceptance training and an enhanced awareness manipulations on cardiovascular responses to a cold pressor test. For independent effects, we expected our brief acceptance training to mitigate cardiovascular responses to the cold pressor test
(Hypothesis 1) whereas our enhanced awareness manipulation would heighten such responses (Hypothesis 2). Consistent with Monitor and Acceptance Theory (Lindsay &
Creswell, 2017), we expected an interactive effect of awareness and acceptance such that participants assigned to the “acceptance training + enhanced awareness” condition would display lower cardiovascular reactivity than participants assigned to the “no acceptance training + enhanced awareness” condition (Hypothesis 3). Our results did not support
Hypothesis 1 or 2, as the acceptance training and enhanced awareness manipulations were unrelated to the magnitude of cardiovascular responses to the CPT on their own.
However, results partially supported Hypothesis 3 such that participants assigned to the
“acceptance training + enhanced awareness” condition displayed lower RSA and TPR reactivity to the CPT than participants assigned to the “no acceptance training + enhanced awareness” condition. Contrary to Hypothesis 3, participants assigned to the “acceptance training + enhanced awareness” condition displayed greater CO reactivity to the CPT than participants assigned to the “no acceptance training + enhanced awareness” condition. Finally, the interaction of acceptance and awareness did not predict SBP, DBP, or PEP reactivity to the CPT. 39
In the present study, the enhanced awareness manipulation and acceptance training interacted to predict RSA, CO and TPR, supporting the interactive framework proposed by Monitor and Acceptance Theory (Lindsay & Creswell, 2017). Significant 3- way interactions revealed a consistent pattern where the contrasts between acceptance training and no acceptance training was significant among individuals assigned to the enhanced awareness condition but not among individuals assigned to the no enhanced awareness condition. In other words, the effects of the acceptance training were stronger under conditions of enhanced awareness. This result implies that heightened awareness may be necessary for acceptance to buffer cardiovascular stress responses. Of interest, this interaction pattern (i.e., where the effect of acceptance is stronger when awareness is high relative to low) is consistent with prior work examining the association between self-reported mindfulness and emotional regulation strategies (Desrosiers, Vine, Curtiss,
& Klemanski, 2014) as well as symptom internalization (Cortazar & Calvete, 2019). For example, Desrosiers et al., (2014) found that self-reported acceptance was negatively associated with rumination and worry, and that this association was strongest when self- reported awareness was high. Similarly, Cortazar and Calvete (2019) found that greater trait acceptance was associated with fewer self-reports of anxious/depressed symptoms only at high levels of trait awareness. In summary, the present study contributes to the literature by replicating the interactive effect of mindful awareness and acceptance in the context of experimentally induced acceptance/awareness states and cardiovascular reactivity to acute stress. 40
Nevertheless, the interactive effects of acceptance and awareness were not consistent across cardiovascular outcomes. In particular, blood pressure and PEP responses did not differ by condition. To evaluate these results, it is important to note that
SBP, DBP, CO, TPR, RSA, and PEP were selected as co-primary outcomes because they index interrelated yet distinct aspects of cardiovascular activation. SBP and DBP index maximum and minimum blood pressure, respectively; CO and TPR index cardiac and vascular activity, respectively, and each contributes to blood pressure. Finally, PEP indexes sympathetic control over the heart, whereas RSA indexes parasympathetic control over the heart. Accordingly, asynchronous reactivity in these parameters is meaningful and may be used to identify distinct profiles of cardiovascular activation
(e.g., Blascovich & Tomaka, 1996).
With respect to CO, TPR, PEP, SBP, and DBP, the present findings fit well within the biopsychosocial model of challenge and threat (Blascovich, 2008a; Blascovich
& Tomaka, 1996). This model states that individuals’ evaluations of demands and resources associated with motivated performance tasks result in psychological states of relative challenge or threat, and that such states produce predictable patterns of physiological activation which are implicated in stress-resilience (see Seery, 2011 for a review). More specifically, challenge states occur when evaluation of resources exceed demands and are indexed by greater CO and lower TPR reactivity. In contrast, threat states result from evaluations of demands exceeding resources, and are indexed by lower
CO and greater TPR reactivity. Moreover, both challenge and threat states lead to increased heart rate and PEP. This is because both challenge and threat states result in 41 sympathetic-adrenal-medullary (SAM) axis activation, direct innervation of the heart muscle and venous tissue, and increased heart rate and PEP. During challenge states, only the SAM axis is activated, thus resulting in unhindered peripheral release of epinephrine from the adrenal medulla, vasodilation of muscle skeletal beds, and decreased TPR as well as increased CO. In contrast, threat states are characterized by co-activation of the
SAM and HPA axes. This is important because HPA axis activation is expected to interfere with peripheral release of epinephrine, resulting in increased TPR and decreased
CO (Seery, 2011). Finally, this model does not consider blood pressure to be indicative of challenge or threat states because both higher TPR and higher CO can contribute to increased blood pressure. Accordingly, threat/challenge states are not expected to differentially influence acute blood pressure responses. In summary, the biopsychosocial model of challenge and threat (Blascovich, 2008a) implies that threat and challenge states may be distinguished on the basis of CO and TPR but not PEP, SBP, or DBP.
Based on the biopsychosocial model of challenge and threat (Blascovich, 2008a) and the pattern of results from the current investigation, the “no acceptance training + enhanced awareness” condition may have led to relatively more threat than challenge states during the CPT than the “acceptance training + enhanced awareness” (and the “no acceptance training + no enhanced awareness”) condition. Of interest, challenge and threat states are thought to reflect stress resilience and vulnerability, respectively.
Cardiovascular profiles indexing threat are hypothesized to contribute to poor cardiovascular health by straining coronary arteries (Blascovich, 2008b). More generally, a meta-analysis examined CO reactivity across 7 studies and found no association with 42 future cardiovascular disease risk (r = .004; Chida & Steptoe, 2010). In contrast, increased resting TPR and heightened TPR reactivity to physical exercise are characteristic of older (Uchino, Holt-Lunstad, Bloor, & Campo, 2005) and hypertensive individuals (Mayet, 2003). Nevertheless, more work is needed to establish the association between challenge/threat cardiovascular response profiles and long-term cardiovascular health outcomes.
Of interest, the effect of study conditions on CO reactivity was moderated by both sex and CPT immersion duration, such that the 3-way interaction of awareness x acceptance x sampling occasion was amplified among males and among individuals who kept their hand submerged for longer. Multiple explanations were considered for these findings. The biopsychosocial model of challenge and threat states that task engagement is a prerequisite for states of challenge or threat (Blascovich, 2008b). Thus, to the extent that males and individuals who kept their hand submerged longer displayed greater task engagement during the CPT, underlying cardiovascular profiles indexing challenge/threat should be more salient. However, challenge/threat states are indexed by both CO and
TPR, and neither sex nor CPT immersion duration moderated the effect of study conditions on TPR reactivity. Alternatively, it may be that brief mindfulness manipulations were more effective for males than females. Nevertheless, documented sex differences in mindfulness intervention effects imply that mindfulness practice is more beneficial for women (Chen et al., 2010; Rojiani et al., 2017). Finally, it may be that exposure to the enhanced awareness manipulation was confounded by CPT immersion duration, such that individuals who displayed greater pain tolerance also received a 43 greater “dose” of the awareness manipulation. Future work would benefit from measuring task engagement and standardizing the duration of the enhanced awareness manipulation to further investigate these results.
Although the biopsychosocial model of challenge and threat does not directly make predictions about RSA reactivity, RSA results may also imply that study conditions influenced how the cold pressor test was perceived. Prior work implies that RSA reliably decreases in response to potent stressors like the Trier Social Stress Test (e.g.,
Shahrestani, Stewart, Quintana, Hickie, & Guastella, 2015). This is because vagal influence on the sinoatrial node (i.e., indexing parasympathetic control of the heart) is reduced during stressful episodes. In the present study, RSA reactivity was moderated by study conditions such that the “no acceptance training + enhanced awareness” condition led to relatively greater RSA reactivity (i.e., a larger stress-induced decrease) than the
“acceptance training + enhanced awareness” and the “no acceptance training + no enhanced awareness” conditions. Accordingly, RSA results may imply that participants assigned to “no acceptance training + enhanced awareness” condition found the cold pressor test relatively more threatening. Consistent with this claim, a recent extension of the biopsychosocial model of challenge and threat (Uphill, Rossato, Swain, & O’Driscoll,
2019) predicts that challenge states should produce relatively smaller decreased in RSA than threat states. The authors argue that this is because diminished RSA reactivity is associated with optimal coping and engagement with environmental perturbations
(Beauchaine, 2001; Porges, 2007) and may therefore index greater relative challenge.
Nevertheless, limited and mixed support exists for the relationship between 44 challenge/threat states and RSA reactivity (e.g., Quigley, Barrett, & Weinstein, 2002). In summary, more work is necessary to establish a relationship between challenge/threat psychological states and RSA reactivity. Future work in this area may benefit from including self-report measures of challenge and threat (e.g., pre-stressor appraisals).
More generally, the current results add to a growing literature examining the effects of mindfulness on RSA. Prior work found that meditation can increase RSA relative to a resting baseline (e.g., Ditto, Eclache, & Goldman, 2006; Krygier et al., 2013) and increase RSA recovery from acute stress (e.g., Azam et al., 2015). Moreover, Paz,
Zvielli, Goldstein, and Bernstein (2017) found that a brief intervention focusing on present moment acceptance and awareness led to diminished RSA reactivity to a stressful hyperventilation task relative to a control condition. The present study adds to this literature by suggesting that the combination of acceptance training and enhanced awareness leads to lower RSA reactivity than enhanced awareness without acceptance training.
In relation to blood pressure, the present study partially replicated prior work.
More specifically, Lindsay et al., (2018) found that mindfulness training focusing on awareness and acceptance led to lower SBP reactivity to the Trier Social Stress Test than awareness-only training and an active control condition, but they found no effect on DBP reactivity. Together, these previous and current results imply that additional replication will be necessary to tease apart the joint influence of awareness and acceptance on blood pressure. Moreover, direct comparison of the present results with Lindsay et al., (2018) should be conducted with caution due to the numerous methodological distinctions 45 between the two studies (e.g., manipulation duration, stressor type, and sample characteristics). Finally, the present null results in relation to blood pressure may be attributed in part to the reported effects of study condition on CO and TPR (i.e., such that both increased CO and increased TPR contribute to blood pressure responses).
The present study was the first to use a 2 x 2 between-subject design manipulating both awareness and acceptance such that all combinations of the awareness/acceptance conditions could be contrasted. This is important because this design allows for the relative utility of the “acceptance training + no enhanced awareness” condition to be evaluated. Standardized mindfulness interventions dedicate a significant amount of time to enhancing one’s awareness of present moment experiences (e.g., MBSR; Kabat-Zinn
& Santorelli, 1999). On its own, this practice is thought to benefit individuals outside of stressful episodes by enhancing positive experiences and improving cognitive functioning in affectively neutral contexts (Lindsay & Creswell, 2017). During stressful episodes, enhanced awareness is thought to amplify affective reactivity and acceptance negates this effect (such that training in both awareness and acceptance is expected to diminish stress reactivity relative awareness-only training and no training). However, it may be that training in acceptance alone yields even greater stress buffering effects than training in awareness and acceptance because it may operate without needing to negate the effects of enhanced awareness (albeit at the cost of losing the benefits of enhanced awareness in positive/neutral contexts). In other words, training in acceptance alone could be especially beneficial in the context of acute stressors. The present study is the first to test this claim and was unable to distinguish the effect of acceptance alone (i.e., acceptance 46 training + no enhanced awareness) on cardiovascular responses from that of other conditions (with the exception of CO reactivity, though health implications of this result are likely limited). In summary, training in acceptance alone does not appear to outperform training in acceptance combined with enhanced awareness in the context of acute stress.
Finally, results do not imply that the cardiovascular response pattern exhibited by the “acceptance training + enhanced awareness” condition were distinguishable from those of the “no acceptance training + no enhanced awareness” condition. This contrast is important because the “no acceptance training + no enhanced awareness” condition is the closest equivalent to an active control condition in the present study (where participants reviewed neutral information about typical stress responses and monitored the time of day during the cold pressor test). Accordingly, results imply that there was no advantage of training in acceptance and enhanced awareness over an active control condition. This result is inconsistent with past studies where the combination of awareness and acceptance produced effects that were distinguishable from active (Lindsay et al., 2018;
Paz et al., 2017) and passive (Chin et al., 2019) control conditions. Multiple explanations may be considered for this finding. First, providing neutral information about typical stress responses may have been more adaptive than anticipated. Consistent with this view, prior work implies that stress responses are commonly perceived negatively (e.g., from a deficit approach; Liu & Vickers, 2015) and that reframing the perceived consequences of stress responses can influence acute cardiovascular stress responses
(Liu, Vickers, Reed, & Hadad, 2017). Second, it may be that, for stress-related outcomes, 47 the disadvantage of awareness-only training (relative to awareness and acceptance) is evident almost immediately whereas the advantage of awareness + acceptance training
(relative to a control) is evident after more elaborate training. Consistent with this claim, prior work implies that mindful acceptance develops more slowly than mindful awareness (Baer, Carmody, & Hunsinger, 2012), suggesting that acceptance may be more difficult to manipulate. Replicating the present study while including other (e.g., passive) control conditions and/or while using a lengthier acceptance manipulation may be necessary to further examine the relative advantage of training in awareness and acceptance.
Some limitations of the present study are worth noting. First, the sample was comprised of healthy college students, thus limiting generalizability. Second, while constraining awareness and acceptance to a single domain (i.e., physiological responses to the cold pressor test) increased experimental control, it may limit the generalizability of the present findings to other mindfulness manipulations. Specifically, mindfulness interventions commonly target present moment experiences indiscriminately, thus allowing mindfulness skills to be applied to a broader range of stressor dimensions than the present study. Related to this limitation, the enhanced awareness manipulation presented fictional temperature readings during the cold pressor task. This may be problematic because 1) participants were more aware of a fictional dimension of the stressor (rather than actual temperature readings) and 2) the enhanced awareness procedure manipulated a representational form of stressor awareness (temperature readings) rather than an experiential form (the actual feeling of one’s hand becoming 48 colder). Accordingly, the generalizability of the present enhanced awareness manipulation to other mindful awareness manipulations is questionable. Using a different feedback procedure (e.g., sound of one’s heart beating) and using actual feedback may be necessary to address these limitations. Third, the duration of the awareness manipulation was dependent upon how long participants kept their hand submerged during the cold pressor test. Accordingly, the awareness manipulation was confounded with pain tolerance and statistically controlling for cold pressor test immersion duration (as was done in the present study) may not fully address this issue. Replicating the present study using an awareness manipulation that is independent of pain tolerance is therefore warranted. Complicating this issue, state awareness manipulations like the one presently used are bound to depend on stressor duration (i.e., enhanced state awareness of the stressor ends when the stressor ends). As such, future studies may need to standardize stressor duration or use other awareness manipulations to address this limitation.
49
Conclusion
The present study tested the independent and interactive effects of a brief acceptance training and an enhanced awareness manipulation on cardiovascular reactivity to a social evaluative cold pressor test. Results implied that enhanced awareness without acceptance training led to greater RSA and TPR reactivity, as well as lower CO reactivity than both acceptance training with enhanced awareness and neither acceptance training nor enhanced awareness. These results support the claim that awareness-only manipulations can heighten stress responses and add to a growing body of work suggesting that awareness-only training and awareness + acceptance training lead to distinguishable effects on some stress-related cardiovascular outcomes.
50
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Tables and Figures
Table 1. Characteristics of the final sample by condition. Characteristic Full Acceptance Training No Acceptance Training Acceptance Training No Acceptance Training Condition Sample + + + + Comparison (N = 202) Enhanced Awareness Enhanced Awareness No Enhanced Awareness No Enhanced Awareness Statistics (N = 51) (N = 51) (N = 50) (N = 50) N % N % N % N % N % Sex Male 72 (35.6%) 18 (35.3%) 18 (35.3%) 18 (36.0%) 18 (36.0%) X2(3,202) = 0.011 Female 130 (64.4%) 33 (64.7%) 33 (64.7%) 32 (64.0%) 32 (64.0%) Race X2(15,202) = 12.72 Asian 7 (3.4%) 2 (4.0%) 1 (2.0%) 2 (4.0%) 2 (4.0%) Black/African American 19 (9.4%) 3 (6.0%) 7 (13.7%) 4 (8.0%) 5 (10.0%) White/Caucasian 170 (84.2%) 46 (90.0%) 40 (78.4%) 41 (82.0%) 43 (86.0%) Multiracial 4 (2.0%) 0 (0.0%) 2 (4.0%) 2 (4.0%) 0 (0.0%) Middle Eastern 1 (0.5%) 0 (0.0%) 0 (0.0%) 1 (2.0%) 0 (0.0%) Other 1 (0.5%) 0 (0.0%) 1 (2.0%) 0 (0.0%) 0 (0.0%) Ethnicity X2(3,202) = 1.34 Hispanic/Latino 9 (4.5%) 1 (2.0%) 2 (4.0%) 3 (6.0%) 3 (6.0%) Not Hispanic/Latino 193 (95.5%) 50 (98.0%) 49 (96.0%) 47 (94.0%) 47 (94.0%) Education Level X2(15,202) = 14.24 High School 9 (4.5%) 3 (5.9%) 2 (3.9%) 4 (8.0%) 0 (0.0%) Some College 31 (15.3%) 9 (17.7%) 4 (7.9%) 9 (18.0%) 9 (18.0%) Junior College 144 (71.3%) 35 (68.6%) 40 (78.4%) 32 (64.0%) 37 (74.0%) Bachelor’s Degree 3 (1.4%) 0 (0.0%) 1 (1.9%) 2 (4.0%) 0 (0.0%) Some Graduate School 14 (7.0%) 4 (7.8%) 4 (7.8%) 3 (6.0%) 3 (6.0%) Graduate Degree 1 (0.5%) 0 (0.0%) 0 (0.0%) 0 (0.0%) 1 (2.0%) Practiced Yoga X2(3,202) = 1.371 Yes 42 (20.7%) 8 (15.7%) 12 (23.5%) 10 (20.0%) 12 (24.0%) No 160 (79.3%) 43 (84.3%) 39 (76.5%) 40 (80.0%) 38 (76.0%) M SD M SD M SD M SD M SD Baseline CV outcomes SBP (mmHg) 108.64 (11.08) 108.98 (9.98) 107.00 (13.69) 109.24 (11.03) 109.36 (9.27) F(3,198) = 0.50 DBP (mmHg) 70.25 (8.03) 71.22 (8.3) 68.41 (8.57) 71.12 (7.71) 70.28 (7.41) F(3,198) = 1.33 RSA (ln[ms]2) 6.17 (1.06) 6.20 (1.12) 6.33 (0.96) 6.07 (1.16) 6.11 (1.02) F(3,198) = 0.57 PEP (ms) 110.49 (14.20) 109.69 (11.58) 108.80 (14.44) 110.59 (18.38) 112.96 (11.3) F(3,195) = 0.77 CO (L/min) 4.37 (1.81) 4.33 (1.69) 4.69 (1.91) 4.18 (1.8) 4.28 (1.88) F(3,194) = 0.75 TPR (dynes⋅sec⋅cm-5) 1791.99 (774.07) 1775.09 (739.68) 1624.44 (683.87) 1897.86 (782.32) 1874.36 (873.64) F(3,194) = 1.28 Age (years) 19.12 (1.19) 19.11 (1.05) 19.15 (1.20) 19.14 (1.06) 19.08 (1.44) F(3,197) = 0.04 Caffeine use (cups) 0.53 (0.79) 0.63 (0.87) 0.33 (0.51) 0.62 (0.95) 0.57 (0.75) F(3,197) = 1.57 Tobacco use (cigarettes) 0.01 (0.14) 0.00 (0.00) 0.00 (0.00) 0.04 (0.28) 0.00 (0.00) F(3,197) = 1.00 Alcohol use (drinks) 0.04 (0.35) 0.06 (0.42) 0.07 (0.56) 0.02 (0.14) 0.00 (0.00) F(3,196) = 0.49 Physical activity (hours) 1.77 (1.52) 1.96 (1.67) 1.85 (1.56) 1.66 (1.22) 1.61 (1.61) F(3,150) = 0.44 Yoga practice (Likert) 1.62 (1.09) 1.41 (0.75) 1.63 (1.07) 1.62 (1.15) 1.82 (1.30) F(3,198) = 1.18 Notes: No between-condition comparison statistics were significant. Baseline CV outcomes refers to cardiovascular estimates obtained during the pre-task rest period of the experiment. Yoga practice was assessed on an 8-point Likert scale. 63
Table 2. Temporal contrasts of cardiovascular parameters. SBP DBP RSA (mmHg) (mmHg) (ln[ms]2) Contrasts B 95% CI b 95% CI b 95% CI pre-task rest v. pre-task manip -2.83* [-4.22, -1.45] -1.31* [-2.58, -0.05] 0.06 [-0.03, 0.16] pre-task rest v. CPT 11.31* [9.93, 12.70] 11.13* [9.86, 12.40] -0.30* [-0.40, -0.20] pre-task rest v. post-task rest -1.70* [-3.09, -0.32] -0.009 [-1.27, 1.25] 0.22* [0.12, 0.32] pre-task rest v. post-task survey 0.30 [-1.07, 1.69] 1.73* [0.46, 2.99] -0.14* [-0.24, -0.04] pre-task manip v. CPT 14.15* [12.76, 15.53] 12.45* [11.18, 13.71] -0.36* [-0.47, -0.26] pre-task manip v. post-task rest 1.12 [-0.25, 2.51] 1.30* [0.04, 2.57] 0.16* [0.06, 0.25] pre-task manip v. post-task survey 3.14* [1.75, 4.52] 3.04* [1.78, 4.31] -0.21* [-0.30, -0.11] CPT v. post-task rest -13.02* [-14.40, -11.63] -11.14* [-12.40, -9.87] 0.53* [0.42, 0.63] CPT v. post-task survey -11.00* [-12.39, -9.62] -9.40* [-10.66, -8.13] 0.15* [0.05, 0.26] post-task rest v. post-task survey 2.01* [0.62, 3.40] 1.74* [0.47, 3.00] -0.37* [-0.46, -0.27] PEP CO TPR (ms) (L/min) (dynes⋅sec⋅cm-5) Contrasts B 95% CI b 95% CI b 95% CI pre-task rest v. pre-task manip -1.16 [-3.24, 0.91] -0.05 [-0.10, 0.001] -27.98 [-65.08, 9.28] pre-task rest v. CPT -1.87 [-3.97, 0.22] 0.25* [0.20, 0.31] 123.40* [85.82, 160.98] pre-task rest v. post-task rest 0.84 [-1.23, 2.92] -0.07* [-0.13, -0.02] 15.51 [-21.82, 52.85] pre-task rest v. post-task survey 1.62 [-0.45, 3.71] -0.05* [-0.10, -0.003] 28.74 [-8.59, 66.08] pre-task manip v. CPT -0.70 [-2.80, 1.38] 0.31* [ 0.25, 0.36] 151.39* [113.87, 188.91] pre-task manip v. post-task rest 2.01 [-0.06, 4.09] -0.02 [-0.07, 0.02] 43.50* [6.22, 80.78] pre-task manip v. post-task survey 2.79* [0.71, 4.87] 0.003 [-0.04, 0.05] 56.73* [19.45, 94.01] CPT v. post-task rest 2.72* [0.62, 4.81] -0.33* [-0.39, -0.28] -107.89* [-145.4, -70.3] CPT v. post-task survey 3.50* [1.40, 5.60] -0.30* [-0.36, -0.25] -94.65* [-132.2, -57.11] post-task rest v. post-task survey 0.78 [-1.29, 2.86] 0.02 [-0.02, 0.08] 13.23 [-24.07, 50.53] Notes: CPT = Cold Pressor Test; manip = manipulation. * p < .05 64
Figure 1. Laboratory visit timeline.
Numerical values shown are minutes since stressor onset (ECG = Electrocardiography; ICG = Impedance cardiography; CPT =
Cold Pressor Test; Accept. Training = Acceptance Training; Aware. Manip. = Awareness Manipulation). 65
Figure 2. Temporal effects across study conditions.
Predicted values of SBP (panel a), DBP (panel b), RSA (panel c), PEP (panel d), CO
(panel e), and TPR (panel f) as a function of sampling occasion. Mean estimates were adjusted for sex (centered on males), as well as BMI, CPT immersion duration, and caffeine/tobacco/alcohol consumption (mean centered). Outlying values were removed prior to deriving model predicted mean estimates.
66
Figure 3. Main effect of acceptance training.
Predicted values of SBP (panel a), DBP (panel b), RSA (panel c), PEP (panel d), CO
(panel e), and TPR (panel f) as a function of sampling occasion and levels of the acceptance manipulation (Accept = acceptance training; Non-Accept = no acceptance training). Mean estimates were adjusted for sex (centered on males), as well as BMI, CPT immersion duration, and caffeine/tobacco/alcohol consumption (mean centered).
Outlying values were removed prior to deriving model predicted mean estimates.
67
Figure 4. Main effect of enhanced awareness manipulation.
Predicted values of SBP (panel a), DBP (panel b), RSA (panel c), PEP (panel d), CO
(panel e), and TPR (panel f) as a function of sampling occasion and levels of the awareness manipulation (Aware = enhanced awareness; Non-Aware = no enhanced awareness). Mean estimates were adjusted for sex (centered on males), as well as BMI,
CPT immersion duration, and caffeine/tobacco/alcohol consumption (mean centered).
Outlying values were removed prior to deriving model predicted mean estimates.
68
69
Figure 5. Interactive effects of awareness and acceptance conditions.
Predicted values of SBP (panels a.1 and a.2), DBP (panels b.1 and b.2), RSA (panels c.1 and c.2), PEP (panels d.1 and d.2), CO (panels e.1 and e.2), and TPR (panels f.1 and f.2) as a function of sampling occasion and assignment to the awareness (Aware = enhanced awareness; Non-Aware = no enhanced awareness) and acceptance (Accept = acceptance training; Non-Accept = no acceptance training) manipulations. Left panels contrast the levels of the acceptance training condition among individuals assigned to the enhanced awareness condition whereas right panels contrast the levels of the acceptance training condition among individuals assigned to the no enhanced awareness condition. Mean estimates were adjusted for sex (centered on males), as well as BMI, CPT immersion duration, and caffeine/tobacco/alcohol consumption (mean centered). Outlying values were removed prior to deriving model predicted mean estimates.
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Appendix A: Acceptance Training Scripts
Acceptance Training Script - Acceptance
“You are about to complete the ice water immersion portion of the experiment.
However, before you do, we would like you to consider how you should approach your physiological reactions to these tasks (e.g., your heart rate is likely to speed up).
Specifically, we would like you to be accepting of your physiological reactions throughout the rest of the experiment. In short, this means that you should make no attempt to avoid, escape, or change your physiological reactions. Just let them be and allow them to be whatever they are. Previous studies found that adopting an attitude of acceptance towards your body’s response to stress can make you better able to handle stressful situations (Eifert & Heffner, 2003).
Nevertheless, some people define acceptance in different ways. So as to give you a better idea of what we mean by acceptance in the context of the present experiment, we will now present you with a metaphor commonly used to describe acceptance—the
Chinese finger trap. If you’ve never seen one, finger traps are woven bamboo tubes. You place your index fingers in either end, and when you try to pull them out, the tube constricts, trapping your fingers. When you push your fingers inward, it causes them to loosen.
Please grab the finger trap in front of you and experiment with it. Place your index fingers on either end and try to pull them away. Notice how the finger trap tightens.
Now try to push your indexes towards the trap. Notice how the finger trap loosens. 71
In most cases, human beings want to minimize pain and discomfort. While some people enjoy extreme temperatures, endurance sports, and pushing their body to its limits, it’s very rare that anyone enjoys anxiety or physical tension. Unfortunately, the inner experiences we want to escape—our bodily sensations—are typically the hardest to get away from. When we try to get away from bodily pain or tension, our body may tighten up on us, like the woven bamboo finger traps. Sometimes the struggle with this tension can make things worse, not better. But when we lean into our discomfort, as when we gently press our index fingers into the finger trap, we create some space. In other words, leaning into discomfort doesn’t free you—you’re still in the trap—but you gain some wiggle room. A desire to pull away is natural—it tends to be our default—but it often gets you stuck.
When we accept, we let go of the struggle against what we’re feeling—in this very moment. In the next moment, we get a choice about what to do next. Acceptance frees us from the struggle with pain and allows for new possibilities. When your entire focus is on getting away from pain, this leaves few alternatives. If you’re willing to accept pain—even for a single moment—you’ve expanded your options.
In summary, as you try to be accepting of your physiological reactions during the upcoming task, keep the analogy of the Chinese finger trap in mind. Make no attempt to avoid, escape, or change your physiological reactions; just let them be and evolve on their own.”
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Acceptance Training Script – Control
You are about to complete the ice water immersion portion of the experiment.
However, before you do, we would like you to review some information about the body’s typical response to stress.
When someone experiences a stressful event, the amygdala, an area of the brain that contributes to emotional processing, sends a distress signal to the hypothalamus. This area of the brain functions like a command center, communicating with the rest of the body through the nervous system so that the person has the energy to fight or flee.
The hypothalamus is a bit like a command center. This area of the brain communicates with the rest of the body through the autonomic nervous system, which controls involuntary body functions such as breathing, blood pressure, heartbeat, and the dilation or constriction of key blood vessels and small airways in the lungs called bronchioles. The autonomic nervous system has two components, the sympathetic nervous system and the parasympathetic nervous system. The sympathetic nervous system functions like a gas pedal in a car. It triggers the fight-or-flight response, providing the body with a burst of energy so that it can respond to perceived dangers. The parasympathetic nervous system acts like a brake. It promotes the rest-and-digest response that calms the body down after the danger has passed.
After the amygdala sends a distress signal, the hypothalamus activates the sympathetic nervous system by sending signals through the autonomic nerves to the adrenal glands. These glands respond by pumping the hormone epinephrine (also known 73 as adrenaline) into the bloodstream. As epinephrine circulates through the body, it brings on a number of physical changes. The heart beats faster than normal, pushing blood to the muscles, heart, and other vital organs. Pulse rate and blood pressure go up. The person undergoing these changes also starts to breathe more rapidly. Small airways in the lungs open wide. This way, the lungs can take in as much oxygen as possible with each breath.
Extra oxygen is sent to the brain, increasing alertness. Sight, hearing, and other senses become sharper. Meanwhile, epinephrine triggers the release of blood sugar and fat from temporary storage sites in the body. These nutrients flood into the bloodstream, supplying energy to all parts of the body.
As the initial surge of epinephrine subsides, the hypothalamus activates the second component of the stress response system — known as the HPA axis. This network consists of the hypothalamus, the pituitary gland, and the adrenal glands.
The HPA axis relies on a series of hormonal signals to keep the sympathetic nervous system going, or the "gas pedal" pressed down, so to speak. If the brain continues to perceive something as dangerous, the hypothalamus releases corticotropin- releasing hormone (CRH), which travels to the pituitary gland, triggering the release of adrenocorticotropic hormone (ACTH). This hormone travels to the adrenal glands, prompting them to release cortisol throughout the body. As a result, the body stays revved up and on high alert. When the threat passes, cortisol levels fall. The parasympathetic nervous system — the body’s "brake" — then dampens the stress response. 74
Appendix B: Acceptance Manipulation Check Questions
Manipulation Check Questions – Acceptance
The Chinese finger trap analogy is meant to illustrate: a) Acceptance b) Dexterity c) Avoidance d) Control
(Next page will display feedback and the correct answer) “You are Correct. Acceptance was the right answer.” OR “Incorrect. Acceptance was the right answer.”
Being accepting of something means: a) Loving it b) Escaping from it c) Trying to change it d) Letting it be
(Next page will display feedback and the correct answer) “You are Correct. Letting it be was the right answer.” OR “Incorrect. Letting it be was the right answer.”
During the upcoming tasks I should try to: a) Be accepting of my physiological reactions b) Avoid my physiological reactions c) Control my physiological reactions d) Think of something I enjoy in life
(Next page will display feedback and the correct answer) “You are Correct. Be accepting of my physiological reactions was the right answer.” OR “Incorrect. Be accepting of my physiological reactions was the right answer.”
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Acceptance Use Questionnaire
1. During the cold-water immersion task, to what degree were you able to remain accepting of your experiences?
(not at all) (somewhat) (very much) 1 2 3 4 5
2. During the rest period following the cold-water immersion task, to what degree were you able to remain accepting of your experiences?
(not at all) (somewhat) (very much) 1 2 3 4 5
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Appendix C: Random Assignment and Psychological Measures
The success of random assignment was further evaluated with respect to trait mindfulness, perceived stress, depressive symptoms, habitual coping strategies, optimism, pain catastrophizing, and pain resilience. Descriptive and reliability statistics of all scales listed are presented in Supplemental Table S-1. In addition, a full copy of all scales listed may be found at the end of this Appendix.
Measures
Trait mindfulness. Trait mindfulness was measured using two scales. The
Philadelphia Mindfulness Scale (PHMS; Cardaciotto, Herbert, Forman, Moitra, &
Farrow, 2008) was considered the primary mindfulness scale because it involves two subcomponents (i.e., awareness and acceptance) which directly correspond with Monitor and Acceptance Theory (Lindsay & Creswell, 2017). Additionally, the Five Facet
Mindfulness Questionnaire (FFMQ; Baer, 2006) was used to measure characteristics of mindfulness beyond awareness and acceptance.
The PHMS (Cardaciotto et al., 2008) is a 20-item scale. Participants were instructed to rate the frequency at which they experience a series of 20 statements using a
5-point scale (1 = Never, 5 = Very Often). The PHMS includes two subscales: 1) awareness and 2) acceptance. Thus, scores on this scale were average separately for each sub-scale where greater scores indicate greater levels of trait mindful awareness/acceptance. 77
The FFMQ (Baer, 2006) is a 39-item scale. Participants were instructed to rate the degree to which a series of 39 statements are “generally true” using a 5-point scale (1 =
Never or very rarely true, 5 = Very Often or always true). The FFMQ includes 5 subscales: 1) observing, 2) describing, 3) acting with awareness, 4) non-judgment, and 5) non-reactivity. As such, average scores for each subscale were computed separately.
Perceived stress. Perceived Stress over the last month was measured using the
Perceived Stress Scale (PSS; Cohen, Kamarck, & Mermelstein, 1983). This scale consists of 10 items rated on a 5-point scale (0 = never, 4 = very often). Scores on this scale were summed.
Depressive symptoms. Depressed mood over the past week was assessed with the Center for Epidemiologic Studies Depression Scale (CES-D; Radloff, 1977).
Participants were asked to indicate “the number for each statement which best describes how often you felt or behaved this way-DURING THE PAST WEEK” (e.g., during the past week, I was bothered by things that usually don't bother me) using the following scale: 1 = rarely or none of the time (less than 1 Day), 4 = most or all of the time (3-7 days). This scale consists of 20 items; scores on this scale were summed.
Habitual coping strategies. Habitual coping strategies was measured using the
28-item brief COPE inventory (Carver, 1997). Participants were asked to report how often they engage in various types of coping strategies on a 4-point scale (1 = I haven't been doing this at all; 4 = I've been doing this a lot). This scale is comprised of 14 subscales each indicating a distinct form of coping. These include: active coping, 78 planning, positive reframing, acceptance, humor, religion, use of emotional support, use of instrumental support, self-distraction, denial, venting, substance use, behavioral disengagement, and self-blame. Consistent with prior work (Wilson, Pritchard, &
Revalee, 2005), the 14 coping strategies measured by the Brief Cope were grouped into an emotion-focused coping subscale (i.e., substance use, use of emotional support, venting, positive reframing, humor, acceptance, religion, and self-blame), a problem- focused coping subscale (i.e., active coping, use of instrumental support, and planning), or avoidant coping subscale (i.e., distraction, denial, behavioral disengagement).
Optimism. Optimism was measured using the 12-item Life Orientation Test
(LOT; Scheier & Carver, 1985). Participants were asked to rate the degree to which they agree with a series of statements on a 5-point scale (0 = Strongly disagree; 4 = Strongly agree). All items were average to derive a total optimism scores with the exception of 4 filler items.
Pain catastrophizing. Pain catastrophizing was measured using the 13-item pain catastrophizing scale (Sullivan, Bishop, & Pivik, 1995). Participants were asked to rate the degree to which they “have these thoughts and feelings when experiencing pain” on a
5-point scale (0 = Not at all; 4 = All the time). The pain catastrophizing scale includes three subscales: rumination, magnification, and helplessness. An average score for each subscale was computed separately.
Pain resilience. Pain resilience was measured using the Pain Resilience Scale
(Slepian, Ankawi, Himawan, & France, 2016). Participants were asked to rate the degree 79 to which they experience a series of statements on a 5-point scale (0= Not at all; 4 = All the time). The pain resilience scale is composed of two subscales: cognitive/affective positivity and behavioral perseverance. As such, sum scores were computed separately for each subscale; a total score was also computed by summing all scale items.
Results
As shown on Supplemental Table S-1, study conditions did not differ on the basis of trait mindfulness, perceived stress, depressive symptoms, habitual coping strategies, optimism, pain catastrophizing, or pain resilience (all ps >.05).
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Supplemental References
Baer, R. A. (2006). Using Self-Report Assessment Methods to Explore Facets of
Mindfulness. Assessment, 13(1), 27–45.
https://doi.org/10.1177/1073191105283504
Cardaciotto, L., Herbert, J. D., Forman, E. M., Moitra, E., & Farrow, V. (2008). The
Assessment of Present-Moment Awareness and Acceptance: The Philadelphia
Mindfulness Scale. Assessment, 15(2), 204–223.
https://doi.org/10.1177/1073191107311467
Carver, C. S. (1997). You want to measure coping but your protocol’ too long: Consider
the brief cope. International Journal of Behavioral Medicine, 4(1), 92.
https://doi.org/10.1207/s15327558ijbm0401_6
Cohen, S., Kamarck, T., & Mermelstein, R. (1983). A Global Measure of Perceived
Stress. Journal of Health and Social Behavior, 24(4), 385–396.
Lindsay, E. K., & Creswell, J. D. (2017). Mechanisms of mindfulness training: Monitor
and Acceptance Theory (MAT). Clinical Psychology Review, 51, 48–59.
https://doi.org/10.1016/j.cpr.2016.10.011
Radloff, L. S. (1977). The CES-D Scale A Self-Report Depression Scale for Research in
the General Population. Applied Psychological Measurement, 1(3), 385–401.
https://doi.org/10.1177/014662167700100306 81
Scheier, M. F., & Carver, C. S. (1985). Optimism, coping, and health: Assessment and
implications of generalized outcome expectancies. Health Psychology, 4(3), 219–
247. https://doi.org/10.1037/0278-6133.4.3.219
Slepian, P. M., Ankawi, B., Himawan, L. K., & France, C. R. (2016). Development and
Initial Validation of the Pain Resilience Scale. The Journal of Pain: Official
Journal of the American Pain Society, 17(4), 462–472.
https://doi.org/10.1016/j.jpain.2015.12.010
Sullivan, M. J. L., Bishop, S. R., & Pivik, J. (1995). The Pain Catastrophizing Scale:
Development and Validation. Psychological Assessment, 7(4), 524–532.
https://doi.org/10.1037/1040-3590.7.4.524
Wilson, G. S., Pritchard, M. E., & Revalee, B. (2005). Individual differences in
adolescent health symptoms: the effects of gender and coping. Journal of
Adolescence, 28(3), 369–379. https://doi.org/10.1016/j.adolescence.2004.08.004 82
Supplemental Tables
Table S-1. Psychological characteristics of the final sample by condition. Characteristic Reliability Full Acceptance Training No Acceptance Training Acceptance Training No Acceptance Training Condition (α) Sample + + + + Comparison (N = 202) Enhanced Awareness Enhanced Awareness No Enhanced Awareness No Enhanced Awareness Statistics (N = 51) (N = 51) (N = 50) (N = 50) Trait Mindfulness PHMS - Acceptance .869 3.66 (0.51) 3.61 (0.47) 3.74 (0.51) 3.64 (0.50) 3.63 (0.57) F(3,198) = 0.59 PHMS - Awareness .785 3.10 (0.68) 3.17 (0.69) 3.02 (0.60) 3.26 (0.68) 2.97 (0.71) F(3,198) = 1.90 FFMQ - Observe .773 3.35 (0.61) 3.28 (0.60) 3.37 (0.59) 3.45 (0.56) 3.31 (0.68) F(3,198) = 0.79 FFMQ - Describe .890 3.29 (0.72) 3.31 (0.63) 3.38 (0.74) 3.16 (0.75) 3.31 (0.78) F(3,198) = 0.78 FFMQ - Act Aware .858 3.11 (0.68) 3.14 (0.60) 3.25 (0.57) 3.01 (0.76) 3.01 (0.76) F(3,198) = 1.48 FFMQ - Non-Judge .913 3.32 (0.80) 3.19 (0.84) 3.42 (0.75) 3.30 (0.78) 3.38 (0.82) F(3,198) = 0.84 FFMQ - Non-React .752 3.11 (0.54) 3.06 (0.50) 3.23 (0.50) 3.10 (0.51) 3.05 (0.62) F(3,198) = 1.23 Perceived Stressa .866 19.09 (6.31) 19.15 (6.84) 18.27 (6.11) 20.20 (5.37) 18.76 (6.82) F(3,198) = 0.84 Depressive Symptomsa .911 15.05 (10.09) 16.09 (10.83) 12.80 (8.61) 16.02 (9.02) 15.34 (11.57) F(3,198) = 1.19 Habitual Coping Strategies Emotion-Focused Coping .799 2.14 (0.46) 2.17 (0.51) 2.11 (0.41) 2.15 (0.45) 2.14 (0.48) F(3,198) = 0.13 Problem-Focused Coping .768 2.48 (0.60) 2.53 (0.62) 2.43 (0.58) 2.40 (0.59) 2.55 (0.63) F(3,198) = 0.73 Avoidant Coping .704 1.71 (0.45) 1.77 (0.47) 1.58 (0.40) 1.78 (0.49) 1.71 (0.43) F(3,198) = 2.12 Optimism .823 2.27 (0.66) 2.20 (0.64) 2.30 (0.75) 2.20 (0.63) 2.36 (0.63) F(3,198) = 0.68 Pain Catastrophizing Rumination .900 4.82 (3.92) 4.88 (3.90) 5.13 (4.20) 4.48 (3.49) 4.80 (4.14) F(3,198) = 0.23 Magnification .725 3.03 (2.66) 3.39 (2.64) 2.86 (2.75) 3.14 (2.70) 2.76 (2.57) F(3,198) = 0.57 Helplessness .867 4.68 (4.32) 5.52 (4.92) 4.13 (3.96) 4.90 (3.93) 4.18 (4.34) F(3,198) = 1.19 Pain Resilience Cognitive/Affective Positivitya .852 13.90 (3.88) 13.88 (3.76) 13.86 (3.38) 14.02 (4.07) 13.84 (4.38) F(3,198) = 0.02 Behavioral Perseverancea .918 21.65 (7.30) 22.15 (6.99) 21.19 (7.11) 21.48 (7.85) 21.80 (7.42) F(3,198) = 0.16 Total Pain Resiliencea .919 35.55 (9.98) 36.03 (9.49) 35.05 (8.73) 35.5 (10.81) 35.64 (11.01) F(3,198) = 0.83 Notes: PHMS = Philadelphia Mindfulness Scale; FFMQ = Five Facet Mindfulness Questionnaire. No between-condition comparison statistics were significant. a Denotes sum scores. 83
Appendix D: Multilevel Model Equations
Prototypical Equations for Tests of Hypothesis 1
The following equation outlines the multilevel model use to predict CO as a function of sampling occasion and acceptance condition. One should note that while CO is presented as an outcome for illustrative purposes, the same model equations were used to predict SBP, DBP, RSA, PEP and TPR.
Level 1: COsi = β0i + β1i(dt_1si) + β2i(dt_2si) + β3i(dt_3si) + β4i(dt_4si) + εsi (1a)
Level 2: β0i = γ00 + γ01(accepti) + U0i (1b)
β1i = γ10 + γ11(accepti) (1c)
β2i = γ20 + γ21(accepti) (1d)
β3i = γ30 + γ31(accepti) (1e)
β4i = γ40 + γ41(accepti) (1f)
Where COsi is the CO value recorded on sampling occasion s for individual i; dt_1si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the pre-task manipulation (i.e., 0 = pre-task rest; 1 = pre-task manipulation); dt_2si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the cold pressor test (i.e., 0
= pre-task rest; 1 = cold pressor test); dt_3si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the post- 84 task rest (i.e., 0 = pre-task rest; 1 = post-task rest); dt_4si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the post-task surveys (i.e., 0 = pre-task rest; 1 = post-task surveys); accepti is a dummy coded variable indicating whether individual i was assigned to the no acceptance training or the acceptance training condition (i.e., 0 = no acceptance training; 1 = acceptance training).
Prototypical Equations for Tests of Hypothesis 2
The following equation outlines the multilevel model use to predict CO as a function of sampling occasion and awareness condition.
Level 1: COsi = β0i + β1i(dt_1si) + β2i(dt_2si) + β3i(dt_3si) + β4i(dt_4si) + εsi (2a)
Level 2: β0i = γ00 + γ01(awarei) + U0i (2b)
β1i = γ10 + γ11(awarei) (2c)
β2i = γ20 + γ21(awarei) (2d)
β3i = γ30 + γ31(awarei) (2e)
β4i = γ40 + γ41(awarei) (2f)
Where COsi is the CO value recorded on sampling occasion s for individual i; dt_1si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the pre-task manipulation (i.e., 0 = pre-task rest; 1 = pre-task manipulation); dt_2si is a dummy coded variable indicating whether sampling 85 occasion s for individual i corresponded to the pre-task rest or the cold pressor test (i.e., 0
= pre-task rest; 1 = cold pressor test); dt_3si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the post- task rest (i.e., 0 = pre-task rest; 1 = post-task rest); dt_4si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the post-task surveys (i.e., 0 = pre-task rest; 1 = post-task surveys); awarei is a dummy coded variable indicating whether individual i was assigned to the no enhanced awareness or the enhanced awareness condition (i.e., 0 = no enhanced awareness; 1 = enhance awareness).
Prototypical Equations for Tests of Hypothesis 3
The following equation outlines the multilevel model use to predict CO as a function of sampling occasion, the acceptance condition, the awareness condition and the interaction of the acceptance and awareness conditions.
Level 1: COsi = β0i + β1i(dt_1si) + β2i(dt _2si) + β3i(dt _3si) + β4i(dt _4si) + εsi (3a)
Level 2: β0i = γ00 + γ01(accepti) + γ02(awarei) + γ03(accepti)*(awarei) + U0i (3b)
β1i = γ10 + γ11(accepti) + γ12(awarei) + γ13(accepti)*(awarei) (3c)
β2i = γ20 + γ21(accepti) + γ22(awarei) + γ23(accepti)*(awarei) (3d)
β3i = γ30 + γ31(accepti) + γ32(awarei) + γ33(accepti)*(awarei) (3e)
β4i = γ40 + γ41(accepti) + γ42(awarei) + γ43(accepti)*(awarei) (3f)
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Where COsi is the CO value recorded on sampling occasion s for individual i; dt_1si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the pre-task manipulation (i.e., 0 = pre-task rest; 1 = pre-task manipulation); dt_2si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the cold pressor test (i.e., 0
= pre-task rest; 1 = cold pressor test); dt_3si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the post- task rest (i.e., 0 = pre-task rest; 1 = post-task rest); dt_4si is a dummy coded variable indicating whether sampling occasion s for individual i corresponded to the pre-task rest or the post-task surveys (i.e., 0 = pre-task rest; 1 = post-task surveys); accepti is a dummy coded variable indicating whether individual i was assigned to the no acceptance training or the acceptance training condition (i.e., 0 = no acceptance training; 1 = acceptance training); awarei is a dummy coded variable indicating whether individual i was assigned to the no enhanced awareness or the enhanced awareness condition (i.e., 0 = no enhanced awareness; 1 = enhanced awareness).
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Appendix E: Supplemental Interaction Tests
Sex x Acceptance x Awareness x Sampling Occasion
The interaction of sex x acceptance x awareness x sampling occasion was significant when predicting CO (F(4,714) = 4.31, p = .002), remained significant when excluding covariates from the model (F(4,746) = 4.35, p = .001), but was non-significant when reintroducing outliers (F(4,724) = 1.12, p = .34), or both excluding covariates and including outlying values (F(4,756) = 1.43, p = .21). Follow-up tests revealed that the interaction of sex x acceptance x awareness x sampling occasion was significant for contrasts of pre-task resting levels of CO and CPT levels (b = -.63, t(1,714) = 3.12, p =
.002, 95% CI [-1.02, -0.23]); no other sampling occasion contrasts referencing pre-task resting levels were significant (all ps > .39). To fully tease apart this 4-way interaction, the 3-way interactions of sampling occasion x acceptance x awareness were examined among males and females.
Among males, the acceptance by awareness interaction was associated with the change from pre-task resting levels of CO to the CPT (b = 0.83, t(1,714) = 5.11, p < .001,
95% CI [0.51, 1.16]). Consistent with Supplemental Figure 1, among males assigned to the enhanced awareness manipulation, the acceptance training condition led to significantly larger increases in CO from the pre-task rest to the CPT than the no acceptance training condition (b = 0.68, t(1,714) = 5.72, p < .001, 95% CI [0.45, 0.91]).
In contrast, among males assigned to the no enhanced awareness condition, assignment to 88 the acceptance training condition did not predict pre-task rest to CPT changes in CO (b =
-.15, t(1,714) = 1.37, p = .17, 95% CI [-0.37, 0.07]).
Among females, the acceptance by awareness interaction was not associated with the change from pre-task resting levels of CO to the CPT (b = -0.20, t(1,714) = 1.75, p =
.081, 95% CI [-0.43, 0.03]). Consistent with Supplemental Figure 1, among females assigned to the enhanced awareness condition, the acceptance training condition did not lead to significantly larger increases in CO from the pre-task rest to the CPT than the no acceptance training condition (b = 0.14, t(1,714) = 1.74, p = .081, 95% CI [-0.02, 0.30]).
Similarly, among females assigned to the no enhanced awareness condition, assignment to the acceptance training condition did not predict pre-task rest to CPT changes in CO (b
= -.06, t(1,714) = 0.74, p = .46, 95% CI [-0.23, 0.10]).
The interaction of sex x acceptance x awareness x sampling occasion was non- significant when predicting SBP (F(4,734) = 0.40, p = .80), DBP (F(4,734) = .46, p =
.76), RSA (F(4,718) = 1.13, p = .34), PEP (F(4,718) = .63, p = .64), and TPR (F(4,711) =
0.55, p = .70). Removing covariates from the model and/or reintroducing outlying values did not alter these findings.
CPT Immersion Duration x Acceptance x Awareness x Sampling Occasion
The interaction of CPT immersion duration x acceptance x awareness x sampling occasion was significant when predicting CO (F(4,712) = 3.16, p = .013), remained significant when excluding covariates from the model (F(4,742) = 3.10, p = .015), reintroducing outlying values (F(4,722) = 3.34, p = .010), or both excluding covariates 89 and including outlying values (F(4,752) = 3.57, p = .006). Follow-up tests revealed that the interaction of CPT immersion duration x acceptance x awareness x sampling occasion was significant for contrasts of pre-task resting levels of CO and CPT levels (b = 0.0055, t(1,712) = 2.28, p = .023, 95% CI [0.0007, 0.0103]); no other sampling occasion contrasts referencing pre-task resting levels were significant (all ps > .36). To fully tease apart this
4-way interaction, the 3-way interactions of sampling occasion x acceptance x awareness were examined at high (+1 SD), mean (average), and low (-1SD) levels of CPT immersion duration.
At high (+1 SD) levels of CPT immersion duration, the acceptance by awareness interaction was associated with the change from pre-task resting levels of CO to the CPT
(b = 0.62, t(1,712) = 4.43, p < .001, 95% CI [0.34, 0.89]). Consistent with Supplemental
Figure 2, among individuals assigned to the enhanced awareness condition who submerged their hand in cold water for a long duration (+1 SD), the acceptance training condition led to significantly larger increases in CO from the pre-task rest to the CPT than the no acceptance training condition (b = 0.48, t(1,712) = 5.50, p < .001, 95% CI
[0.31, 0.66]). In contrast, for participants assigned to the no enhanced awareness condition who submerged their hand in cold water for a long duration (+1 SD), assignment to the acceptance training condition did not predict pre-task rest to CPT changes in CO (b = -.13, t(1,712) = 1.22, p = .22, 95% CI [-0.34, 0.08]).
At mean (average) levels of CPT immersion duration, the acceptance by awareness interaction was associated with the change from pre-task resting levels of CO 90 to the CPT (b = 0.39, t(1,712) = 4.09, p < .001, 95% CI [0.20, 0.58]). Consistent with
Supplemental Figure 2, among individuals assigned to the enhanced awareness condition who submerged their hand in cold water for an average duration (mean), the acceptance training condition led to significantly larger increases in CO from the pre-task rest to the
CPT than the no acceptance training condition (b = 0.30, t(1,712) = 4.42, p < .001, 95%
CI [0.17, 0.43]). In contrast, for participants assigned to the no enhanced awareness condition who submerged their hand in cold water for an average duration (mean), assignment to the acceptance training condition did not predict pre-task rest to CPT changes in CO (b = -.09, t(1,712) = 1.35, p = .17, 95% CI [-0.22, 0.04]).
Finally, at low (-1 SD) levels of CPT immersion duration, the acceptance by awareness interaction was not associated with the change from pre-task resting levels of
CO to the CPT (b = 0.16, t(1,712) = 1.24, p = .21, 95% CI [-0.09, 0.43]). Consistent with
Supplemental Figure 2, among individuals assigned to the enhanced awareness condition who submerged their hand in cold water for a short duration (-1 SD), the acceptance training condition did not lead to significantly larger increases in CO from the pre-task rest to the CPT than the no acceptance training condition (b = 0.11, t(1,712) = 1.20, p =
.22, 95% CI [-0.07, 0.30]). Similarly, for participants assigned to the no enhanced awareness condition who submerged their hand in cold water for a short duration (-1 SD), assignment to the acceptance training condition did not predict pre-task rest to CPT changes in CO (b = -.05, t(1,712) = 0.56, p = .57, 95% CI [-0.24, 0.13]). 91
The interaction of sampling occasion x acceptance x awareness x CPT immersion duration was non-significant when predicting SBP (F(4,733) = 1.08, p = .36), DBP
(F(4,734) = 0.63, p = .97), RSA (F(4,717) = .20, p = .93), PEP (F(4,718) = 1.10, p = .35), and TPR (F(4,711) = .50, p = .73). Removing covariates from the model and/or reintroducing outlying values did not alter these findings.
92
Supplemental Figures
Supplemental Figure 1. Predicted values of cardiac output as a function of sampling occasion, awareness (Aware = enhanced awareness; Non-Aware = no enhanced awareness), acceptance (Accept = acceptance training; Non-Accept = no acceptance training), and biological sex. Left panels contrast the levels of the acceptance training condition among individuals assigned to the enhanced awareness manipulation for males
(panel a.1) and females (panel b.1). Right panels contrast the levels of the acceptance training condition among individuals assigned to the no enhanced awareness condition for males (panel a.2) and females (panel b.2). Mean estimates were adjusted for BMI,
CPT immersion duration, and caffeine/tobacco/alcohol consumption (mean centered).
Outlying values were removed prior to deriving model predicted mean estimates. 93
Supplemental Figure 2. Predicted values of cardiac output as a function of sampling occasion, awareness (Aware = enhanced awareness; Non-Aware = no enhanced awareness), acceptance (Accept = acceptance training; Non-Accept = no acceptance training), and CPT immersion duration. Left panels contrast the levels of the acceptance training condition among individuals assigned to the enhanced awareness manipulation for individuals who kept their hand in cold water for low (-1 SD; panel a.1), mean
(average; panel b.1), and high (+1SD; panel c.1) durations. Right panels contrast the levels of the acceptance training condition among individuals assigned to the no enhanced awareness condition for individuals who kept their hand in cold water for low 94
(-1 SD; panel a.2), mean (average; panel b.2), and high (+1SD; panel c.2) durations.
Mean estimates were adjusted for sex (centered on males), as well as BMI, and caffeine/tobacco/alcohol consumption (mean centered). Outlying values were removed prior to deriving model predicted mean estimates.
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