Identifying Potential Barriers to Physical Activity

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Identifying Potential Barriers to Physical Activity Adherence: Anxiety Sensitivity and Body Mass as Predictors of Fear During Exercise Jasper A. J. Smits a; Candyce D. Tart a; Katherine Presnell a; David Rosenfield a; Michael W. Otto b a Department of Psychology, Southern Methodist University, Dallas, Texas b Department of Psychology and Center for Anxiety and Related Disorders, Boston University, Boston, Massachusetts, USA First Published on: 12 August 2009

To cite this Article Smits, Jasper A. J., Tart, Candyce D., Presnell, Katherine, Rosenfield, David and Otto, Michael W.(2009)'Identifying

Potential Barriers to Physical Activity Adherence: Anxiety Sensitivity and Body Mass as Predictors of Fear During Exercise',Cognitive Behaviour Therapy,99999:1, To link to this Article: DOI: 10.1080/16506070902915261 URL: http://dx.doi.org/10.1080/16506070902915261

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Cognitive Behaviour Therapy iFirst article, pp. 1–9, 2009

Identifying Potential Barriers to Physical Activity Adherence: Anxiety Sensitivity and Body Mass as Predictors of Fear During Exercise Jasper A. J. Smits1, Candyce D. Tart1, Katherine Presnell1, David Rosenfield1 and Michael W. Otto2 Department of Psychology, Southern Methodist University, Dallas, Texas; 2Department of Psychology and Center for Anxiety and Related Disorders, Boston University, Boston, Massachusetts, USA

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Abstract. A growing body of work suggests that obese adults are less likely to adhere to exercise than normal-weight adults because they experience greater levels of discomfort and distress during exercise sessions. The present study introduces and provides a preliminary test of the hypothesis that the distress experienced during exercise among persons with elevated body mass index is particularly high among those who fear somatic arousal (i.e. elevated anxiety sensitivity [AS]). Young adults were randomly assigned to complete 20 min of treadmill exercise (at 70% of their age-adjusted predicted maximum heart rate) or 20 min of rest. Body mass, AS, and negative affect were measured at baseline, and fear was measured at 4-min intervals during the experimental phase. Consistent with the authors’ hypothesis, there was a significant Exercise £ BMI £ ASI interaction (sr 2 ¼ .08), suggesting that the greatest fear levels during exercise were observed among participants with high body mass, but only if they also had elevated AS. These findings offer a new approach for identifying specific vulnerable individuals and have clear clinical implications, given that the amplification factor of AS can be modified with clinical intervention. Key words: exercise; physical activity adherence; body mass index; negative affect; anxiety sensitivity. Received January 29 2009; Accepted March 23 2009 Correspondence address: Jasper A. J. Smits, PhD, Department of Psychology, Southern Methodist University, Dedman College, PO Box 750442, Dallas, TX 75275, USA. Tel: 214-768-4125; Fax: 214768-4191. E-mail: [email protected]

The rate of obesity in the United States is at an epidemic level. Indeed, the 2005–2006 National Health and Nutrition Examination Survey estimated that approximately one third of US adults are obese (body mass index [BMI] ^ 30 kg/m2; Ogden, Carroll, McDowell, & Flegal, 2007). Although not sufficient to produce significant weight loss without additional dietary interventions (Garrow & Summerbell, 1995), regular physical activity has significant health benefits for people at any weight (e.g. reduced all-cause mortality [Lee & Skerrett, 2001], increased longevity [Lee & Paffenbarger, 2001], and reduced risk for coronary heart disease [Kohl, 2001]) and is a critical component q 2009 Taylor & Francis ISSN 1650-6073 DOI: 10.1080/16506070902915261

to long-term weight management (e.g. preventing weight gain, maintaining weight loss; cf. Goldberg & King, 2007). Despite these well-documented benefits, fewer than one in five (18.8% of men; 16.6% of women) of US obese adults meet public health recommendations for physical activity (Centers for Disease Control and Prevention; CDC, 2000). Moreover, once they do initiate a physical activity program, obese adults are less likely to maintain adequate activity levels over time compared with their nonobese counterparts (King et al., 1997, 2006). Initial studies indicate that the decreased rates of exercise adherence among obese adults may be attributed, at least in part, to


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Smits, Tart, Presnell, Rosenfield, and Otto

the experience of negative affective states during exercise sessions. Specifically, Ekkekakis and Lind (2006) found that overweight, relative to normal-weight, women report greater negative affect during prescribed exercise. The importance of negative affect during exercise to long-term exercise adherence has received empirical support in a recent study. Williams and colleagues (2008) measured negative affect before and during a graded submaximal exercise test (i.e. . 64% of age-adjusted predicted maximum heart rate [HRmax]) in a sample of 37 sedentary adults who participated in a larger physical activity promotion trial. The authors found that negative affect experienced during the moderate-intensity exercise predicted physical activity 6 and 12 months later, even after controlling for baseline physical activity and negative affect. The magnitude of the effects was large, with negative affect during exercise explaining 20% of the variance of physical activity levels 6 months later and 12% of the variance 12 months later (Williams et al., 2008). These findings suggest that adoption of adequate physical activity levels may be particularly difficult for obese individuals because they respond to exertion-related symptoms during exercise with negative affect. Recent research has recognized anxiety sensitivity (AS) as a dispositional variable that may identify individuals who are sensitive to the experience of exertion-related symptoms during exercise. AS refers to the tendency to experience fear in response to anxiety-related bodily sensations (e.g. racing heart, sweating, breathlessness; Reiss & McNally, 1985), many of the same sensations experienced during exercise. Individuals who are high in AS often fear these benign bodily sensations because they believe that they have harmful physical (e.g. dying, having a heart attack), psychological (e.g. going crazy, losing control), or social consequences (e.g. embarrassment; Reiss & McNally, 1985). Accordingly, when engaging in moderate-to-vigorous intensity exercise, individuals with elevated levels of AS may experience significantly greater levels of distress compared with their counterparts with low levels of AS, which, in turn, may result in reduced physical activity adoption rates. This relationship should be particularly strong for individuals who experience higher levels of exertion-related

COGNITIVE BEHAVIOUR THERAPY

symptoms, such as those who are obese. Indeed, overweight and obese individuals report higher levels of perceived exertion (Ekkekakis & Lind, 2006) and greater physical discomfort (Deforche, De Bourdeaudhuij, & Tanghe, 2006) during exercise than their normal-weight counterparts. Moreover, obese individuals experience higher kneejoint loads than normal-weight individuals while walking at comparable speeds, which can contribute to greater musculoskeletal pain during exercise (Browning & Kram, 2007). One study found that overweight and obese women were more likely than lean women to experience exercise-interfering medical conditions, including greater skin friction, urinary stress incontinence, varicose veins, foot static and knee pain, the need for insoles, low back pain, and hip arthritis (Hulens, Vansant, Claessens, Lysens, & Muls, 2003). Additionally, obese women reported greater perceived exertion and complained more frequently of dyspnea and musculoskeletal pain during a 6-min walk test than their lean counterparts (Hulens et al., 2003). Thus, research suggests that, in addition to reduced aerobic capacity, obese individuals experience biomechanical difficulties that interfere with exercise as well as greater perceived discomfort and pain during physical activity, which may be further exacerbated by high levels of AS. Indirect support for the role of AS in intensifying distress in response to exerciseinduced symptoms comes from studies that have demonstrated that AS predicts fearful responding to symptom provocation procedures (e.g. voluntary hyperventilation, inhalation of carbon dioxide-enriched air; cf. McNally, 2002). Similarly, AS is linked to distress and avoidance in response to other physical symptoms, such as pain (e.g. Asmundson, Norton, & Veloso, 1999; Zvolensky, Goodie, McNeil, Sperry, & Sorrell, 2000) and dyspnea (Simon et al., 2006). Finally, cross-sectional work indicates that high AS is linked to less physical activity (McWillliams & Asmundson, 2001; Smits & Zvolensky, 2006), suggesting that high-AS individuals may respond more fearfully to physical activity, which then results in exercise avoidance. Taken together, these results indicate that, when exercising, obese individuals will experience more exertion-related symptoms than their normal-weight counterparts, and that AS may


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Fear during exercise

put these individuals at risk for responding to exercise with fear, which, in turn, decreases exercise adherence. Given that regular moderate intensity exercise can provide substantial benefits for improving overall fitness and protection against deleterious health outcomes, targeting barriers to exercise among obese individuals who are currently sedentary is an important focus for health promotion interventions. The present study is the first to test the hypothesis that fear during exercise varies as a function of the interaction between BMI and AS. Participants in this study were healthy college students who were randomly assigned to either 20 min of moderate-intensity exercise or 20 min of rest before taking a single vital capacity inhalation of carbon dioxideenriched air (Smits, Meuret, Zvolensky, Rosenfield, & Seidel, 2009). Negative affect, AS, and BMI were measured at baseline, and fear was measured at 4-min intervals during the exercise (or rest) period as well as immediately after the inhalation procedure. For the present study, we used the baseline data as well as the data collected during the exercise (or rest) period. We predicted that the highest levels of fear would be observed among persons who were likely to experience the greatest levels of exercise-related symptoms (those with an elevated BMI) and who were predisposed to experience these symptoms as aversive (those with elevated AS scores). Hence, we predicted that the interaction between AS and BMI would significantly predict fearful responses during exercise. On the other hand, because no aversive physiological symptoms should be elicited during rest, AS should not exacerbate them, and as such, there should be no interaction between AS and BMI for participants in the rest condition. Thus, we expect a triple interaction among exercise condition (rest vs. exercise), BMI, and ASI.

Method Participants The sample comprised 51 female and 41 male undergraduate students who participated in a randomized controlled study investigating the effects of exercise on emotional responding to a biological challenge (see Smits et al., 2009). The sample was predominantly White (n ¼ 73

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[79%]) and ranged in age from 17 to 24 years (M ¼ 19.43, SD ¼ 1.31). Exclusion criteria included (a) history of panic attacks; (b) substance use disorders within past 6 months; (c) use of psychotropic medications; (d) history of medical conditions that could be aggravated by study procedures (e.g. acute exercise, carbon dioxide challenge), including cardiovascular disorders (e.g. cardiac arrhythmia, cardiac failure), renal disorders, respiratory disorders (e.g. asthma, lung fibrosis), high blood pressure, epilepsy, stroke, and seizures; and (e) pregnant or lactating.

Measures Diagnostic interview. The Structured Clinical Interview for DSM-IV Axis I Disorders NonPatient Edition (SCID-NP; First, Spitzer, Gibbon, & Williams, 1995) was administered to assess psychiatric exclusion criteria (e.g. bipolar disorder, substance use disorders). Graduate students administered the SCID-NP after receiving extensive training in administration and scoring. An independent, trained rater reviewed a random selection of 10% of all audiotaped interviews and revealed no cases of disagreement. Body mass index. BMI (kg/m2) was calculated from directly measured height and weight. Height was measured to the nearest millimeter using a portable direct-reading stadiometer, and weight was assessed to the nearest 0.1 kg using a Tanita (Arlington Heights, IL) TBF300A digital scale, with participants’ shoes, socks, and coats removed. Two measures of height and weight were obtained and averaged for analyses. Cardiorespiratory fitness. The International Physical Activity Questionnaire (IPAQ; Craig et al., 2003) was used to classify participants’ physical activity level according to the fivecategory scale used by Jurca et al. (2005). The IPAQ has demonstrated good retest reliability (r ¼ .66 –.87) and concurrent and criterion validity (Craig et al., 2003). We used the nonexercise test model put forth by Jurca et al. (2005) to estimate cardiorespiratory fitness (CRF). This model estimates a metabolic equivalent level of CRF based on the individual’s physical activity category, gender, age, BMI, and resting heart rate. Baseline negative affect. The Negative Affect subscale of the Positive Affect Negative Affect Schedule (PANAS-NA; Watson,


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Clark, & Tellegen, 1988) is a 10-item self-report instrument that measures the tendency to experience negative affective symptoms. The PANAS-NA asks respondents to indicate on a 5-point Likert scale (1 ¼ very slightly, 5 ¼ extremely) the degree to which they typically felt various negative affective states (e.g. “irritable,” “upset,” “afraid”) in the past week. The PANAS-NA has demonstrated good internal consistency in both clinical and nonclinical samples (a ¼ .85 – .93), retest reliability (r range ¼ .71 for 2 months to .43 for 72 months), as well as convergent and discriminant validity (Watson, 2000). The PANAS-NA was used as a covariate in the analyses. Anxiety sensitivity. The Anxiety Sensitivity Index (ASI; Reiss, Peterson, Gursky, & McNally, 1986) is a 16-item self-report instrument that assesses the fear of anxiety-related somatic and emotional symptoms. Respondents indicate on a 5-point Likert-type scale (0 ¼ very little, 4 ¼ very much) the degree to which they agree with statements of the potential negative consequences of anxiety symptoms (e.g. “When I notice that my heart is beating rapidly, I worry that I might have a heart attack,” “It scares me when I become short of breath”). Scores can range between 0 and 64; scores above 25 indicate possible clinical problems (Peterson & Plehn, 1999, p. 70). The ASI has sound psychometric properties in both clinical and nonclinical samples, including high internal consistency (a ¼ .80–.90; Peterson & Reiss, 1992; Taylor, Koch, & McNally, 1992), good retest reliability (r range ¼ .75 for 2-week periods to .71 for 3-year periods; Peterson & Reiss, 1992; Maller & Reiss, 1992), and good construct validity (McNally & Lorenz, 1987). Peak fear. Participants rated their fear levels at 4-min intervals during the experimental phase (i.e. exercise or rest) using a Subjective Units of Distress Scale (SUDS; Wolpe, 1958); item ratings ranged from 0 (no fear) to 100 (extreme fear). The SUDS is a widely used measure in anxiety research, with adequate psychometric properties (Kaplan, Smith, & Coons, 1995). For the analyses, we used the highest reported fear (SUDS) level.

Procedure Research staff contacted students expressing an interest in the study during classroom screenings. After providing a full description of the study procedures, a staff member


administered the Physical Activity Readiness Questionnaire (Shephard, Cox, & Simper, 1981) and a medical history questionnaire in order to identify participants with any medical or medication contraindications. Medically eligible participants were then administered the IPAQ and scheduled to come to the laboratory to complete the study protocol. On arrival to the laboratory, a research staff member obtained written informed consent and measured the participant’s height and weight and resting heart rate. Subsequently, participants completed self-report measures and were administered the SCID-NP. After eligibility was established, research assistants allocated participants to either the exercise or rest condition using a computer-generated random sequence of conditions blocked by physical activity level (i.e. active vs. inactive). After receiving instructions for the biological challenge procedure, participants in the exercise condition completed 20 min of treadmill exercise and participants in the rest condition sat quietly for 20 min. To control for exertion level, exercise intensity was set at 70% of HRmax (calculated as 220 – age £ .70) for all participants in the exercise condition. The treadmill (Smooth 7.1 HR Pro, InternetFitness.com, Inc., Mt. Laurel, NJ) featured a computer-controlled exercise training management system that received HR input from a Polar (Lake Success, NY) transmitter chest strap. The experimenter progressively increased the speed of the treadmill during a 3-min warm-up until 70% of HRmax was reached and adjusted the speed during the 20-min exercise period to ensure that participants maintained this target HR. SUDS ratings were collected every 4 min in both conditions. All participants completed the biological challenge after a 3-min (additional) rest period. All procedures were approved by the Southern Methodist University Institutional Review Board.

Results Preliminary analyses On average, participants were relatively fit, in the normal weight range, and reported levels of anxiety sensitivity and negative affect in the normative range (Table 1). A series of t tests revealed that the two conditions (exercise vs. rest) did not differ significantly on any of the variables assessed at baseline (e.g. demographic

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Table 1. Descriptives of study variables

Variable

1

2

3

1. BMI 2. CRF 3. PANAS-NA 4. ASI

— 2 .12 .03 2 .11

— 2 .03 2 .14

4

Exercise

Rest

M (SD)

M (SD)

23.65 14.54 12.20 10.31

—

(3.67) (2.26) (2.81) (6.97)

24.43 14.67 13.36 11.50

(4.86) (2.12) (4.01) (7.32)


.51* — Note. Jurca et al. (2005) provided the following interpretation of metabolic equivalent (MET) levels of CRF: 1 MET: resting metabolic rate, sitting quietly in a chair, or 3.5 mL O2 uptake/kilogram body mass/minute; , 3 METs: severely limited functional capacity; 3 –5 METs: highly deconditioned individuals; 10 METs: approximate maximal capacity expected in regularly active middle-aged men and women; 13 METs: excellent prognosis regardless of disease status; 18 METs: elite endurance athletes; 20 METs: world-class athletes. BMI ¼ body mass index; CRF ¼ cardiorespiratory fitness; PANAS-NA ¼ Negative Affect subscale of the Positive Affect Negative Affect Schedule; ASI ¼ Anxiety Sensitivity Index. *p , .01.

characteristics, BMI, CRF, PANAS-NA, ASI, all ps . .11). Among predictor variables, significant correlations were observed between scores on the PANAS-NA and ASI (r ¼ .51, p , .01) but not between ASI and BMI. The BMI and PANAS-NA measures were logtransformed to reduce skewness.

Effect of ASI, BMI, and exercise condition on peak fear We conducted a multiple regression analysis to test the study hypotheses. We regressed peak fear on all three independent variables (BMI, ASI, and exercise condition) and included all the two and three-way interactions between these independent variables in the regression. Exercise was dummy coded such that the exercise condition served as the reference group (i.e. exercise ¼ 0; rest ¼ 1). BMI and ASI were included as continuous variables but were centered at their means

(as suggested by Aiken & West, 1991) to reduce multicollinearity with the interaction terms. The PANAS-NA was included as a covariate to (a) account for random variability in the outcome (fear), thereby increasing the power of the analyses, and (b) control for differences in the outcome that might merely result from initial differences in negative affect (e.g. ASI might be related to fear merely because it is related to negative affect and negative affect is related to fear). All predictor variables were entered into the regression equation simultaneously. Analysis of the residual of the multiple regression indicated that the major assumptions of regression analysis were met: the residual appeared normally distributed and homoscedastic, there were no outliers that strongly impacted the results (Cook’s distance , 1.0 for all cases), and there was no multicollinearity (Variance inflation factors [VIFs] , 2.0). The results are presented in Table 2 and Figure 1. Consistent with hypothesis, the

Table 2. Regression analysis predicting peak fear Predictor PANAS-NA BMI ASI Exercise Exercise £ BMI Exercise £ ASI BMI £ ASI Exercise £ BMI £ ASI

b

ta

p

sr 2

.08 2 .03 .28 .24 .02 .05 2 .51 .40

0.67 2 0.18 1.94 2.50 0.15 0.32 2 3.59 2.76

.500 .860 .060 .010 .880 .750 .001 .007

.00 .00 .04 .07 .00 .00 .13 .08

Note. All predictors were entered simultaneously in the regression equation. PANAS-NA ¼ Negative Affect subscale of the Positive Affect Negative Affect Schedule; BMI ¼ body mass index; ASI ¼ Anxiety Sensitivity Index; Exercise ¼ dummy-coded experimental condition (0 ¼ exercise; 1 ¼ rest). a df ¼ 83:


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Figure 1. The effect of the three-way interaction of BMI £ ASI £ exercise on peak fear. (SUDS ¼ Subjective Units of Distress Scale; BMI ¼ body mass index; ASI ¼ Anxiety Sensitivity Index; Peak Fear ¼ highest level of fear during exercise or rest period; ASI ¼ M is the sample mean of ASI (10.88); ASI ¼ 25 is clinical ASI cutoff; BMI ¼ M is the sample mean of BMI (24.03; normal range); BMI ¼ M þ 1SD is sample mean plus 1 standard deviation (28.30; overweight range); BMI ¼ M þ 2SD is sample mean plus 2 standard deviations (32.57; obese range).

three-way interaction of Exercise £ BMI £ ASI was significant (b ¼ 169.73, t ¼ 2.76, p ¼ .007, sr 2 ¼ .08), suggesting that the interactive effects of BMI £ ASI on fear varied by condition. Following the recommendation by Aiken and West (1991) for graphing interactions involving continuous variables, we graphed the interaction at points that were theoretically relevant to our major hypothesis. Thus, the graph portrays the form of the interaction for those who have higher levels of BMI (from the mean to 2 SD above the mean in BMI) and for those higher in ASI (at the mean and at ASI ¼ 25, clinical levels of ASI). The significance of a two-way interaction (e.g. ASI £ BMI) in a multiple regression that also includes a three-way interaction reflects


the significance of that interaction only for the condition in which the third variable (exercise condition) equals 0 (Aiken & West, 1991). Thus, because the exercise condition was coded 0, the significant BMI £ ASI interaction in this model (sr 2 ¼ .13; see Table 2) indicates that the BMI £ ASI interaction is significant for those in the exercise condition and that the relationship between BMI and fear is indeed moderated by AS among participants in the exercise condition. To test the hypothesis that this interaction was not significant for those in the rest condition, we repeated the prior analysis but changed the dummy coding for the exercise variable such that the rest condition served as the reference group (i.e. exercise ¼ 1; rest ¼ 0; Aiken & West, 1991). Consistent with hypothesis, the ASI £ BMI interaction was not significant in this model ( p ¼ .86). It should be noted that these analyses did not yield a significant Exercise £ ASI interaction, suggesting that the relationship between ASI and fear did not vary by exercise condition (without taking into account the moderating effects of BMI). Our last analysis was identical to the first analysis with the exception that we also entered CRF as a predictor variable. The results indicated that the observed significant relationships remained significant (and nonsignificant relationships remained nonsignificant, at nearly identical p values) after controlling for CRF.

Discussion Regular exercise is a frequently recommended but poorly adopted intervention for obesity (King et al., 1997, 2006). A growing body of research suggests that negative affective states may play an important role in the adoption of physical activity. Cross-sectional research indicates that persons with mental health conditions characterized by negative affect (e.g. major depressive disorder, panic disorder, social phobia, and specific phobia) tend to be less physically active than nonpsychiatric controls (Goodwin, 2003). Furthermore, prospective research has extended these findings by demonstrating that self-reported trait negative affect, anxiety, and depressive symptoms are negatively associated with exercise participation over time, again after accounting for the effects of age and gender


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(de Moor, Beem, Stubbe, Boomsma, & De Geus, 2006; McAuley, Morris, Motl, Hu, Konopack, & Elavsky, 2007). Also, as noted, preliminary longitudinal work suggests that the experience of negative affect during exercise predicts the adoption of physical activity over time (Williams et al., 2008). In the present study, we have expanded the investigation of the role of negative affect during exercise by attending to AS as a potentially important individual difference variable that may identify individuals most at risk for anxiety during exercise, which may lead to greater noncompliance with physical activity recommendations. Consistent with this hypothesis, we found that the impact of fear of arousal sensations on negative affect was greatest for individuals with higher BMI. This finding is consistent with the hypothesis that the impact of AS on fear during exercise may be most important for the subset of individuals likely to experience greater sensations of arousal and exertion during exercise. In our current study, this interaction effect may have been particularly important given that most participants were in the lower ranges of BMI. This may have accounted for the absence of a significantly greater effect of AS on fear among participants in the exercise condition (relative to those in the rest condition), and supports the notion that elevated AS has its most important impact on those who are more likely to experience exertion-related symptoms as a result of excessive weight. A central implication of these findings is that AS may be a particularly important variable for aiding the understanding of exercise avoidance among obese individuals. High AS may make attempts at exercise more aversive because of the amplification of the meaning (aversiveness) of sensations of physical exertion. Because AS is readily modifiable with cognitive behavioral interventions (Smits, Berry, Tart, & Powers, 2008), it seems appropriate to consider the adoption of similar interventions with the goal of increasing the acceptability of exercise and exertion-related sensations among special populations, such as obese individuals. Our research encourages intervention research of this kind. Several limitations deserve mention. In our study, the range of ASI scores was limited. A stronger effect for the predictive significance


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of the ASI on fear during exercise may have been found had more elevated scores been represented in the study. Nonetheless, the finding of a significant Exercise £ BMI £ ASI interaction within the constraints of a limited range of scores speaks to the potential importance of ASI to understanding exerciserelated fear. Further investigation of this relationship in samples with greater elevations in scores may show an even stronger relationship. In addition, we did not directly assess the degree of exertion-related symptoms experienced by participants. BMI scores were used as a proxy for the likelihood of these exertion-related symptoms, and there is evidence that such symptoms are elevated among obese individuals (Browning & Kram, 2007; Ekkekakis & Lind, 2006; Hulens et al., 2003), but we did not independently confirm this relationship. To further support our hypothesized model, future research will need to support a broader causal model showing that obesity is linked to greater physical symptoms during exercise, and that AS serves as an amplification factor for the degree of fear in response to these symptoms, which can lead to correspondingly reduced exercise adherence rates. This future work should also extend our research by examining other negative affective states in addition to fear. Despite these limitations, our current findings have clear clinical implications. We have a tentative model for predicting which individuals may be most susceptible to negative affect during exercise, and we know that the amplification factor of AS can be modified with clinical intervention. As such, this research has the longer term potential of identifying specific individuals in need and offering a new approach for improving the acceptability (reducing the aversiveness) of healthful exercise.

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