Characterizing the affective responses to an acute bout of moderate-intensity exercise among outpatients with schizophrenia

Psychiatry Research 237 (2016) 264–270

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Characterizing the affective responses to an acute bout of moderateintensity exercise among outpatients with schizophrenia Markus J. Duncan a,n, Guy Faulkner a,b, Gary Remington b,c, Kelly Arbour-Nicitopoulos a a

Faculty of Kinesiology & Physical Education, University of Toronto, Toronto, ON, Canada Schizophrenia Program, Centre for Addiction and Mental Health, Toronto, ON, Canada c Department of Psychiatry, University of Toronto, Toronto, ON, Canada b

art ic l e i nf o

a b s t r a c t

Article history: Received 9 June 2015 Received in revised form 3 November 2015 Accepted 15 January 2016 Available online 28 January 2016

In addition to offering many physical health benefits, exercise may help improve mental health among individuals with schizophrenia through regulating affect. Therefore, the purpose of this study is to characterize affective responses experienced before, during and after a 10-min bout of exercise versus passive sitting among individuals with schizophrenia. A randomized crossover design compared affect related to feelings of pleasure and arousal at baseline, 6-min into the task, immediately post-task, and 10 min post-task to sitting. Thirty participants enroled in the study; 28 participants completed the study. Separate mixed model analyses of variance were conducted for pleasure and arousal, with test order as the between-subject factor, and time and task as within-subject factors. For pleasure, a significant main effect for time and a time x task interaction effect emerged. Post-hoc Bonferroni corrected t-tests (α ¼.0125) revealed significant differences between pleasure at baseline and both immediately post-task and 10 min post-task. No other main effects or interactions emerged. Individuals with schizophrenia derive acute feelings of pleasure from exercise. Thus, exercise may provide a method of regulating affect to improve mental health. Future studies should examine the links between affective responses to health behaviours such as long-term adherence to exercise within this population. & 2016 Elsevier Ireland Ltd. All rights reserved.

Keywords: Schizophrenia Exercise Affect Walking Mental health Well-being

1. Introduction Physical activity (PA), such as exercise, may provide multiple health benefits for persons with schizophrenia, such as reducing excess weight, improving glycemic control, and reducing the risk of cardiovascular disease (Scheewe et al., 2013; Stubbs et al., 2015). Several systematic reviews of randomized controlled trials have demonstrated that non-pharmacological interventions for managing weight – including PA – in individuals who have schizophrenia (Faulkner et al., 2007) or who are using antipsychotics (Caemmerer et al., 2012) are plausible and modestly efficacious. In addition to the physical health benefits of PA, systematic reviews and meta-analyses of randomized controlled trials demonstrated small but significant improvements in the mental health of patients with schizophrenia who participate in the assigned PA intervention (Gorczynski and Faulkner, 2010; Rosenbaum et al., 2014; Firth et al., 2015),suggesting that regular PA can not only help prevent and manage physical co-morbidities of schizophrenia, but also may improve psychological symptoms and welln

Corresponding author. E-mail address: [email protected] (M.J. Duncan).

http://dx.doi.org/10.1016/j.psychres.2016.01.030 0165-1781/& 2016 Elsevier Ireland Ltd. All rights reserved.

being. One potential psychological mechanism through which PA may improve mental health is by regulating affect. In a series of papers, Ekkekakis and Petruzzello (2000, 2001a, 2001b, 2002) identify core affect, the fundamental and reflexive feelings of pleasure and arousal that are elicited by exposure to a stimulus, as the ideal target to assess general changes in affect in response to a single acute bout of PA. Specifically Ekkekakis and Petruzzello (2002) advocate for the use of the Circumplex Model of Affect (Russell, 1980; Fig. 1) when assessing core affect, given that it is a dimensional (comprising of pleasure and arousal) and highly parsimonious model, which matches the theorized structure of core affect. Since these recommendations were published, the affective responses to acute bouts of PA in the general population have been well characterized using the Circumplex Model of Affect. Using this model, researchers have shown within the general adult population that individuals tend to feel a greater increase in pleasure after engaging in lower intensity PA than more vigorous intensity PA (Reed and Ones, 2006; Ekkekakis et al., 2011a). During PA, feelings of pleasure tend to be homogenously positive at low intensity, and homogenously negative during more vigorous intensity PA, while at moderate intensities, feelings of pleasure vary considerably by individual, with roughly equal

M.J. Duncan et al. / Psychiatry Research 237 (2016) 264–270

+

ACTIVATION

Post-Exercise

+

−

PostExercise+ Rest − VALENCE Fig. 1. Circumplex model of affect. Note: Arrows depict an approximation of the typical affective response after exercise based on Ekkekakis et al. (2011a).

proportions of participants reporting increases and decreases in pleasure (Ekkekakis et al., 2011a). Feelings of arousal increase during PA but decline over time after PA is ceased, while feelings of pleasure after PA remain elevated (Ekkekakis et al., 2011a). Two studies have examined affective responses to PA among individuals with schizophrenia (Vancampfort et al., 2011; Heggelund et al., 2014); both have observed reductions in self-reported feelings of anxiety and psychological distress were reduced while positive well-being was increased immediately following 20 and 25 min bouts of exercise. However, neither of these studies have examined affect during exercise, which is a concern given that not all individuals may experience exercise as pleasurable in the moment, providing an inaccurate characterization of affect trajectory during exercise (Ekkekakis et al., 2011a) and that feelings during exercise may be related to motivation to continue with a bout of PA (Ekkekakis and Dafermos, 2012). Furthermore, only Heggelund et al. (2014) examined the effects of exercise on core affect using the Positive and Negative Affect Schedule (PANAS), finding an increase in positive activation after exercise. However, this study employed a high-intensity interval training protocol consisting of four 4 min bouts of vigorous intensity on a treadmill interspersed with 3 min moderate intensity breaks, which may not be the most feasible exercise for individuals who are unfamiliar with physical training to undertake on their own, or with minimal instruction. Another pilot study has, however, used the Circumplex Model of Affect to examine affective responses, before, during, and after an acute bout of treadmill walking at a self-selected pace compared to sitting among 14 people with serious mental illness (three participants self-reported schizophrenia) as a secondary outcome, (Arbour-Nicitopoulos et al., 2011). The intensity of each task was assessed objectively using heart rate and subjectively with the Borg Ratings of Perceived Exertion (Borg RPE; Borg, 1998). The 10-min brisk walking induced a significantly higher mean heart rate and Borg RPE score than the sitting condition. Mean Borg RPE during the exercise condition was 9.99, with a range of 6–13.6, suggesting that although some participants had reached moderate-intensity thresholds (ratings from 12–14; Borg, 1998), participants generally perceived the PA as light-intensity. A significant time by condition interaction for pleasure was observed

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(p o.05, partial η2 ¼.19), as well as a main effect for time along the arousal dimension (p o.03, partial η2 ¼.21). Overall, this study demonstrated a trend for increases in activation and valence when participants engaged in brisk walking versus passive sitting. However, having a pre-set, objectively measured intensity level for the exercise condition may help to clarify these results, by reducing variation in the stimulus. Furthermore, using a sample comprised solely of people with schizophrenia will improve the specificity of the results. Common national and international PA guidelines recommend adults engage in 150 min of moderate to vigorous intensity PA per week, in bouts of at least 10 min, in order to reduce the risk of disease (World Health Organization, 2010; Canadian Society of Exercise Physiology, 2012). Brisk walks of 10 min or more at a moderate-intensity, for example, can contribute to meeting these guidelines. Minimally intensive exercise in 10-min bouts may represent an achievable way for individuals with poor physical fitness to begin accruing health benefits from PA. Of note, a recent systematic review of walking interventions for people with schizophrenia (Soundy et al., 2014), suggests small improvements in health factors such as weight, body composition, and waist circumference, with no adverse events reported. Walking also requires minimal equipment and is feasible for most individuals without physical disabilities or other limitations. Brief bouts of walking at moderate-intensity may therefore be a simple and feasible way for individuals with schizophrenia to become physically active. Therefore the purpose of the study is to characterize affect before, during, and after a 10-min bout of treadmill walking on affect among individuals with schizophrenia, compared to passive sitting. It was hypothesized that individuals with schizophrenia will demonstrate the typical pattern of increased arousal during exercise, followed by a decrease in arousal with time after exercise is ceased. Meanwhile, feelings of pleasure were hypothesized to increase after exercise and remain elevated. Affect is not expected to change during the sitting condition.

2. Methods 2.1. Participants Study eligibility required participants to be: (1) age 18–64 years in line with Canadian Physical Activity Guidelines recommendations for adults (Canadian Society of Exercise Physiology, 2012); (2) outpatients with schizophrenia or schizoaffective disorder; and (3) deemed safe to engage in PA as assessed by the Physical Activity Readiness Questionnaire (Canadian Society for Exercise Physiology, 2002). Participants were deemed ineligible to participate if they had: (1) been hospitalized in the past 12 months for angina pectoris, myocardial infarction, or cardiac surgery of any kind; and/or (2) uncontrolled hypertension (defined as blood pressure4 140/90). Participants were recruited from a larger, prospective study examining the determinants of physical activity among individuals with schizophrenia. All participants enroling in the larger study were invited to participate in the present study. Research ethics approval for the present study was obtained from the University of Toronto. Participants provided written consent prior to commencing the study, and capacity to consent was assessed immediately after using the MacArthur Competence Assessment Tool for Clinical Research (MacCAT-CR; Appelbaum and Grisso, 2001) Required sample size calculations were based on the betweenwithin factors (task and time) interaction effect on pleasure was partial η2 ¼0.19 previously observed by Arbour-Nicitopoulos et al. (2011). Based on this effect size with an alpha level of 0.05 and

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power of 0.80, G*Power3 was used to calculate a required sample size of 32 participants across two conditions. To account for the 25% attrition rate reported by Arbour-Nicitopoulos et al. (2011) study, the intended recruitment rate for the present study was 40 participants. 2.2. Materials and measures 2.2.1. Screening measures The Mini-International Neuropsychiatric Interview (MINI) (Sheehan et al., 1998) was used to confirm diagnosis. The MacCATCR (Appelbaum and Grisso, 2001) was used to assess the informed decision making capabilities of each participant wishing to enrol in the current study. The MacCAT-CR is a rigorous and commonly used assessment of capacity to consent and is considered a gold standard for this purpose (Naimark et al., 2006). 2.2.2. Sample descriptors The anchored version of the Brief Psychiatric Rating Scale (BPRS-A; Woerner et al., 1988) and the severity scale of the Clinical Global Impression scale (CGI-S; Guy, 1976) were used as brief assessments of symptom severity. The Apathy Evaluation Scale (AES; Marin et al., 1991) is an 18-item self-report questionnaire, which assesses amotivation – a core negative symptom of schizophrenia. The AES is a reliable questionnaire with good construct validity designed for use with psychiatric populations (Marin et al., 1991). Anhedonia was assessed by the Snaith–Hamilton Pleasure Scale (SHAPS) which was developed to measure anhedonia in psychiatric populations (Snaith et al., 1995). The SHAPS has been shown to be a psychometrically valid measure of hedonic capacity – the ability to experience pleasure (Leventhal et al., 2006). Similarly, the Calgary Depression Scale for Schizophrenia (CDSS), a valid and reliable tool for measuring depression in people with schizophrenia (Addington et al., 1990, 1992), was used to assess current levels of depression. All three scales of negative symptomology compliment the BPRS and CGI as sample descriptors. Current PA levels were assessed using the International Physical Activity Questionnaire (Craig et al., 2003). Use of the IPAQ-SF with people who have schizophrenia has demonstrated acceptable reliability and criterion validity with accelerometry comparable to that of the general adult population (Faulkner et al., 2006). 2.2.3. Affect Pleasure was assessed with the Feeling Scale (FS; Hardy and Rejeski, 1989), which asks participants to rate on an 11-point scale “how well you feel”, ranging from þ5 (very good) to  5 (very bad), with 0 anchored as neutral. Arousal was assessed using a modified version of the Felt Arousal Scale (FAS; Svebak and Murgatroyd, 1985), which required participants to rate on an 11-point scale “how aroused you feel” (i.e. relaxed vs. excitement), ranging from þ5 (high arousal) to  5 (low arousal). Both the FS and the 11-point FAS scales have previously been used to measure affective responses to acute exercise in people with severe mental illness, including schizophrenia (Arbour-Nicitopoulos et al., 2011). 2.2.4. Exercise intensity Percentage of calculated maximum heart rate (HR) was used as an objective measure of exercise intensity during the moderateintensity exercise task. HR was monitored continuously throughout both tasks using a chest strap Polar T31 HR monitor. The Borg Rating of Perceived Exertion (Borg RPE; Borg, 1998), a gold standard measure of perceived exertion, was also used to assess participants' perceived exercise intensity. The Borg RPE is a single scale ranging from 6 (no exertion at all) to 20 (maximal exertion). Values on the scale, when multiplied by 10, are designed to correspond approximately to respondents' HR (Borg, 1998). A rating

of 12–14 on the Borg scale corresponds approximately to moderate-intensity exercise (Hines, 1999). 2.3. Study design The study followed a randomized crossover design. Participants completed both an exercise task and a passive sitting task, in random order, on non-consecutive days within a 1-week period. Randomization was performed by drawing from a deck of 40 cards sealed in opaque envelopes and shuffled by an independent party. Twenty cards were marked to start with the exercise task, while the remaining 20 were marked to start with the sitting task, but were otherwise indistinguishable. Participants were unaware of the process of selection, and were blinded as to which task they had been assigned to until the first session was underway. The experimenter (MD) drew the allocation card on the day of the participant's first visit for the current study. Participants received $15 for participating in the first session, and $20 for participating in the second session to promote study completion. Participants reviewed the affect scales prior to the exercise and sitting tasks. 2.3.1. Exercise task The exercise task consisted of a 2-min warm-up period, followed by 10 min of moderate-intensity walking, followed by a 2-min cool-down at a slower pace. Moderate-intensity for the current study was defined as 64–76% of the calculated maximum HR for each participant (American College of Sports Medicine, 2013). To ensure participants remained within this target HR range, the experimenter adjusted the speed of the treadmill throughout the 10-min moderate-intensity walking period. Prior to commencement, participants were reminded that they must reach a certain HR, based on their personal capacity, and that the speed of the treadmill would be adjusted in order to achieve that HR, as well as how to stop if they did not feel safe or wished to withdraw. The measures of affect and exercise intensity were administered while standing on the treadmill prior to the warm-up (pre-task; 0 min), midway into the task (in-task; 6 min), after the cool-down period while still walking (immediately post-task; 14 min), and 10 min after the cool down while sitting quietly (10min post-task; 24 min). 2.3.2. Sitting During the control testing session, participants were instructed to sit quietly on a chair placed behind the treadmill for 14 min. They were asked not to talk to anyone except in an emergency, or when asked to respond to a scale. The measures of affect and exercise intensity were again assessed at baseline, in-task, immediately post-task, and 10-min post-task. 2.4. Statistical analyses Given that pleasure and arousal are conceptually orthogonal, two separate repeated measures analyses of variance (ANOVA) were used to assess changes in pleasure and arousal as dependent variables, with time (baseline, in-task, immediately post-task, and 10-min post-task) and task (moderate-intensity walking vs. passive sitting) as the within-subjects factors, and testing order (walking/sitting vs. sitting/walking) as the between-subjects factor. Significant results from the ANOVAs were followed up with Bonferroni corrected t-tests, in accordance with the study hypotheses. Namely, affect scores at baseline were compared to affect at the remaining three time points (i.e. in-task, immediately post-task, and 10-min post-task), while affect scores during passive sitting were compared to affect scores during moderate-intensity walking at the four specified time periods. Where necessary, non-sphericity was corrected using the Greenhouse-Geisser

M.J. Duncan et al. / Psychiatry Research 237 (2016) 264–270

correction.

3. Results 3.1. Sample characteristics Forty-five participants from the parent study were approached; of these 10 were not interested, and 5 were unable to participate due to responses on the PAR-Q. As a result, total of 30 participants were recruited for the study, with 28 completing both testing sessions. One participant did not return for the sitting session and another did not complete the exercise protocol. Table 1 describes the final sample (N ¼28). Based on clinical experience this sample was judged to be representative of the general outpatient (schizophrenia) population at the Centre for Addiction and Mental Health in Toronto, although self-reported weekly PA was high. Symptom severity scores ranged from 2 (borderline) to 6 (severely ill) on the CGI-S and 20–48 on the BPRS-A, indicating that symptoms in this sample were generally moderate. Two participants had scores over 6 on the Calgary Depression Scale, indicating that they are likely to have comorbid depression. The majority of participants were overweight or obese (75%). 3.2. Changes in affect during the exercise and passive sitting tasks Table 2 summarizes the mean HR, percent maximum HR, and Borg RPE values obtained by time for each task. During the exercise task, the mean percent maximum HR was within the target HR for moderate-intensity. A mean Borg RPE score of 12 during exercise indicates that the exercise was largely perceived as moderately intense. Results from the repeated measures ANOVA for pleasure revealed no significant main effect for testing order, F(1,26) ¼.54, p ¼.47, or any interactions between testing order and either task, F (1,26)¼ 0.00, p ¼.97; time, F(2.21,57.35)¼ .44, p ¼.67, GreenhouseGeisser correction, ε ¼0.74; or task x time F(2.06, 53.59) ¼1.34, p ¼0.27, Greenhouse-Geisser correction, ε ¼0.69. An overall significant main effect for time emerged, F(2.21,57.35) ¼4.76, p ¼.004, partial η2 ¼ 0.36 Greenhouse-Geisser correction, ε ¼0.74, indicating an increase in pleasure over time. This time effect was superseded by a significant time x task interaction, F(2.06, 53.59) ¼4.86, p¼ .01, Greenhouse-Geisser correction, ε ¼ 0.69, partial η2 ¼0.33. Four post-hoc Bonferroni corrected paired t-tests (α ¼ 0.0125) revealed significant differences between baseline and both post-task (t (27) ¼2.98, p ¼.006) and 10-min post-exercise (t(27) ¼ 4.04, p o.001). Overall, pleasure scores increased post-exercise compared to baseline, with no difference in scores between baseline and in-task. Contrary to our hypothesis, no main effect for task was observed, F(1,26)¼.50, p¼ .49, partial η2 ¼0.02. Fig. 2 displays pleasure scores across time as a function of task. Results from the repeated measures ANOVA for arousal revealed no significant main effect for testing order, F(1,26)¼1.62, p ¼.21, nor were there any interactions between testing order and either task, F(1,26)¼ 3.05, p ¼.10; time, F(3,78) ¼.50, p ¼.68; or task x time, F(2.14,55.66)¼ .39, p ¼.69, Greenhouse-Geisser correction, ε ¼0.71. Contrary to our hypothesis, no overall main effects for task, F(1,26)¼ 2.05, p¼ .17, partial η2 ¼0.07; or time, F (3,78) ¼ 1.38, p ¼.25, partial η2 ¼ 0.05, emerged for arousal, nor was there a significant interaction effect between time x task, F (2.14,55.66)¼ .25, p¼ .79, Greenhouse-Geisser correction, ε ¼0.71, partial η2 ¼0.01. 4. Discussion The present study examined the core affective responses

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Table 1 Summary of participant demographics. Demographic

Value

Male:female Age (years) Mean (SD) Range Symptom severity BPRS mean score (SD) CGI mean score (SD) AES mean score (SD) SHAPS mean score (SD) CDS mean score (SD) Medication use Mean (SD) chlorpromazine equivalents Mean (SD) months on current antipsychotic (n¼ 23) Concomitant anti-depressants Concomitant beta-blockers Concomitant other anxiolytics Concomitant mood stabilizers BMI (kg/m2) Mean (SD) Not available Underweight (BMI o 18.5) Normal weight (18.5 o BMIo 25) Overweight (25 o BMIo 30) Obese (BMI 4 30) Waist circumference Males mean (SD) (n¼ 19) Females mean (SD) (n¼ 7)

20:8

Males with central obesity* Female with central obesity* Minutes MVPA (IPAQ) MVPA mean (SD) min/week Category 1: low Category 2: moderate Category 3: high Could not provide minutes/day Ethnicity White African South Asian Asian Biracial Employment Not employed Part-time Student Other Education Some high school (no diploma) High school diploma At least some Postsecondary Marital status Single Married Smoking habits Current smokers Mean (SD) cigarettes/day (n ¼13)

43.0 (11.5) 28–64 30.5 (7.5) 3.5 (1.2) 30.5 (7.5) 47.4 (5.8) 2.4 (2.6) 606.2 (573.4) 59.4 (51.7) 7 0 8 2 29.6 (6.6) 1 (3.5%) 1 (3.5%) 5 (18%) 9 (32%) 12 (43%) 95.6 (30.0) cm 101.9 (19.1) cm 12 (63.2%) 6 (85.7%) 263.7 (401.9) 11 (39%) 9 (32%) 4 (14%) 4 (14%) 11 (39%) 10 (36%) 4 (14%) 1 (4%) 2 (7%) 15 (54%) 11 (39%) 1 (4%) 1 (4%) 4 (14%) 3 (11%) 21 (75%) 23 (82%) 5 (18%) 17 (61%) 11.7 (7.1)

Note. Values are frequencies unless otherwise specified. BPRS ¼ Brief Psychiatric Rating Scale 18-item anchored version, CGI ¼Clinical Global Impression Severity Scale, AES¼ Apathy Evaluation Scale, SHAPS ¼Snaith–Hamilton Pleasure Scale, CDS¼ Calgary Depression Scale, BMI ¼Body Mass Index, *Central Obesity ethnic and gender specific waist circumference cut offs from (Alberti et al., 2006), MVPA ¼moderate-to-vigorous physical activity, IPAQ¼International Physical Activity Questionnaire.

during and following an acute bout of moderate-intensity walking, using the Circumplex Model of Affect as a theoretical framework, within a sample of individuals with schizophrenia. As expected, pleasure after exercise increased compared to baseline; however, feelings of pleasure did not differ during exercise as compared to baseline, suggesting that the overall increase in pleasure takes place upon completing the exercise. Additionally, there was no overall difference in pleasure scores between sitting and exercise,

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Table 2 Summary of intensity measures for exercise and sitting tasks. Time

Exercise HR (bpm) %Max HR Borg RPE Sitting HR (bpm) %Max HR Borg RPE

Baseline

In-task

Immediate posttask

10-min posttask

94.9 (16.7) 121.5 (10.9) 111.3 (14.2) 53.3 (8.6) 68.4 (5.8) 62.7 (8.6) 8.4 (2.5) 12.0 (3.4) 10.2 (3.4)

89.3 (15.5) 50.5 (8.8) 8.4 (2.8)

86.5 (13.3) 48.6 (6.9) 8.1 (2.9)

83.6 (14.3) 47.0 (7.1) 8.2 (2.9)

86.5 (14.4) 48.6 (7.1) 8.1 (3.2)

85.0 (15.0) 47.7 (7.4) 8.1 (3.2)

Note: Means and (SD), HR ¼Heart Rate, RPE ¼Rating of Perceived Exertion.

indicating that individuals with schizophrenia do not necessarily experience moderate intensity exercise as any more or less pleasant than being sedentary. The lack of difference between sitting and exercise may represent a ceiling effect, given that responses on the FS approached the highest score on the scale, even at baseline, and the anchor for the highest score is only “very good.” If, however, individuals with schizophrenia do not perceive the short bout of exercise as any more pleasurable than sitting quietly, this may, in part, explain the low levels of PA typically observed in individuals with schizophrenia (Cohn et al., 2004; Daumit et al., 2005; Lindamer et al., 2008; Yamamoto et al., 2011; Soundy et al., 2013). Currently, a growing body of knowledge suggests that pleasure experienced during exercise may be related to PA participation in the general population (Rhodes and Kates, 2015). Future research examining whether the pleasure experienced during exercise is predictive of future PA participation in persons with schizophrenia is warranted. Contrary to the hypothesis, arousal responses throughout the exercise bout did not significantly change from baseline nor did they differ from the passive sitting task. While not significant, changes in arousal followed the pattern commonly observed within the affect and acute exercise literature, where arousal increases during exercise, and remains elevated afterwards, but slowly begins to decline with time (Ekkekakis and Petruzzello, 1999; Ekkekakis et al., 2011b). Lack of power may explain why this well established relationship was not observed; however, it may also represent a feature of schizophrenia, or the sedative effects of

antipsychotic medication (Miller, 2004), among other possibilities. Further study is warranted, as changes in activation or arousal may be an important mediator in cognition (Hamann, 2001; MujicaParodi et al., 2002) and may therefore lead to acute cognitive benefits for individuals with schizophrenia. While anhedonia (specifically as an inability to derive pleasure from normally pleasurable stimuli) has long been considered a core symptom of schizophrenia (Kraepelin, 1971; Andreasen, 1982; Blanchard and Cohen, 2006), it has recently been criticized as a diagnostic symptom of schizophrenia (Horan et al., 2006; Foussias and Remington, 2010; Strauss and Gold, 2012; Strauss, 2013). Overall, people with schizophrenia tend to report similar feelings of happiness as individuals without schizophrenia (Agid et al., 2012). They also often experience similar changes in affect in response to affectively relevant stimuli (Kring et al., 1993; Kring and Neale, 1996), and report deriving similar amounts of pleasure from engaging in enjoyable activities (Gard et al., 2007) as individuals without schizophrenia, indicating that people with schizophrenia do experience pleasure in response to pleasurable stimuli. Rather, it has been suggested that dysfunction lies in the ability to anticipate pleasure, especially from goal-directed activities (Klein, 1984; Horan et al., 2006; Gard et al., 2007). Given that the participants in this study experienced changes in feelings of pleasure after engaging in exercise, this is further evidence that consummatory pleasure systems remain intact in schizophrenia. Previously, Heggelund et al. (2014) demonstrated that individuals with schizophrenia experience improvements in positive affect in response to high-intensity interval training for 25 min, with the benefits lasting up to 3 h post-exercise. The current study builds on this literature by demonstrating that feelings of pleasure increase, and remain elevated, after a brief 10-min bout of moderate-intensity walking. While potentially having less health and physical fitness effects than longer, more vigorous bouts of exercise, brisk walking for brief periods of time, as was performed on the treadmill in this study, may be more feasible for individuals inexperienced with PA to do on their own while still improving affect. Encouraging patients to engage in even brief bouts of PA to benefit their mental health is therefore warranted, as it is likely to help people with schizophrenia regulate affect on a daily basis and contribute to overall positive mental well-being. This may be especially important for individuals with schizoaffective disorder or co-morbid depression where affect may be negatively valenced on a regular basis. Future studies may want to examine if the acute

5

Feeling Scale Score

4

3

Exercise

2

1

Sitting

0

Baseline

In-Task

Immediately Pos -Taskt

Time Fig. 2. Changes in pleasure during the exercise and passive sitting tasks.

10-min Post Task

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affective benefits of exercise are greater for individuals with higher ratings of depression, or comorbid depressed mood. Lack of variation in Calgary Depression Scale scores in the current sample prevents such analysis. Additionally, use of mood stabilizers, antidepressants and other affect modifying medication may have confounded current results, however mental comorbidities are common among individuals with schizophrenia. Future studies may seek to exclude individuals taking these medications to reduce confounding variables, or perform sub-analyses with a larger sample to maintain generalizability. In terms of bias, testing order had no effect on any of the affective outcomes. Overall, this suggests low risk of bias due to the randomization and allocation concealment. Furthermore, only two individuals dropped out of the study, and only one of these individuals ceased midway through the exercise protocol. While this may represent feelings of displeasure, this single individual is unlikely to change results significantly. This individual also had the highest individual score on the AES, representing high levels of amotivation, which may represent low levels of interest in completing any goal-directed task, and seemed to be responding to the affective measures at random throughout both the sitting and exercise tasks. In particular high levels of negative symptoms correlate with lower levels physical activity and autonomous motivation for physical activity among individuals with schizophrenia (Vancampfort et al., 2012, 2015). Given that exercise may help decrease negative symptoms with longer term interventions (Gorczynski and Faulkner, 2010; Rosenbaum et al., 2014; Firth et al., 2015), despite being a barrier to participating in PA, the relationship between affective response to PA and negatives symptoms such as apathy as a potential mediator of symptom change or covariate of the affective response is warranted. Overall, the sample reported high levels of weekly PA, and thus may not be representative of the general schizophrenia outpatient population who tend to be less physically active (Cohn et al., 2004; Daumit et al., 2005; Lindamer et al., 2008; Yamamoto et al., 2011; Soundy et al., 2013). It is reasonable to assume that individuals who agree to be in a study to do physical activity are likely to be more active, or at least receptive to the possibility of doing more PA. However, while the IPAQ is reliable as a self-reported measure (Faulkner et al., 2006), it is not likely to be as accurate as a more objective measure of PA such as accelerometry; this short fall along with social desirability may also, in part, explain the high levels of PA reported by participants. Future research should examine whether inactive participants, verified a priori by accelerometry as opposed to self-report, demonstrate similar responses, as these results may only apply to relatively active outpatients. Furthermore, due to the contextual and temporary nature of core affect, it is unclear if the same test would reliably elicit a similar result if retested on another occasion, and longer-term follow-up is warranted in future studies. In sum, individuals with schizophrenia experienced the expected pattern of feeling more pleasant affect post-exercise. Therefore, it appears that people with schizophrenia can potentially accrue increases in pleasure after only a 10-minute session of moderate-intensity exercise, indicating that small bouts of moderate-intensity exercise may serve as a method for regulating affect on a daily basis. However, individuals also experienced the sitting condition as pleasant. This points to the possibility that the lower rates of PA participation typically reported in this population might be explained in part by PA not being experienced as more pleasant than inactive options. Further research is needed to confirm this possibility. Contributors Mr. Duncan designed the study and wrote the protocol under

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the supervision of Dr. Arbour-Nicitopolous, Dr. Faulkner, and Dr. Remington. Mr. Duncan undertook the statistical analysis, and wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript.

Conflict of interest Dr. Remington has received research support from Novartis, Medicure and Neurocrine Bioscience, consultant fees from Laboratorios Farmacéuticos ROVI, Synchroneuron, and Novartis, and speaker's fees from Novartis. The other authors have no conflicts to disclose.

Acknowledgements This work was supported by a Canadian Institutes of Health Research (Grant no. 492855) operating grant (PI: G. Faulkner) and an Ontario Graduate Scholarship (to M. Duncan). Guy Faulkner holds a Canadian Institutes of Health Research-Public Health Agency of Canada (CIHR-PHAC) Chair in Applied Public Health. These funding sources had no further role in study design, statistical analysis or interpretation of findings; in writing of the manuscript; or in the decision to submit for publication.

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