EFFECT OF IMPLEMENTATION INTENTIONS TO CHANGE BEHAVIOUR: MODERATION BY INTENTION STABILITY 1

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1 Psychological Reports, 2010, 106, 1, Psychological Reports 2010 EFFECT OF IMPLEMENTATION INTENTIONS TO CHANGE BEHAVIOUR: MODERATION BY INTENTION STABILITY 1 GASTON GODIN Canada Research Chair on Behaviour and Health Laval University ARIANE BÉLANGER-GRAVEL, STEVE AMIREAULT Department of Social and Preventive Medicine Laval University MARIA-CECILIA B. J. GALLANI Department of Nursing, Faculty of Medical Sciences State University of Campinas MARIE-CLAUDE VOHL Department of Food Science and Nutrition Laval University LOUIS PÉRUSSE Department of Social and Preventive Medicine Laval University Summary. tion intentions on leisure-time physical activity, taking into account the stability of intention. At baseline (T 0 ), 349 participants completed a psychosocial questionnaire and were randomly assigned to implementation intention or control condition. Three months after baseline assessment (T 1 ), participants in the experimental group were asked to plan where, when, and how they would exercise. Leisure-time physical activity was assessed 3 mo. later (i.e., at 6-mo. follow-up; T 2 ). The intervention had no signifi vity at 6-mo. follow-up. However, a significant interaction of group and intention stability was observed, with the effect of the intervention on behaviour statistically significant only among those with unstable intention. Intention stability thus moder rvention, i.e., the intervention was more successful among individuals who needed support to change (unstable intenders). Regular physical activity is positively associated with many health benefits and mounting evidence supports its role in the prevention of several chronic diseases, including coronary artery disease, stroke, Type 2 diabetes, hypertension, osteoporosis, and colon and breast cancer (Warburton, Nicol, & Bredin, 2006; Warburton, Katzmarzyk, Rhodes, & Shepard, 2007). However, regardless of these benefits, it is estimated that about 50 to 75% of the adult population in North America do not reach the amount of physical activity recommended by public health authorities (Cameron, Craig, & Paolin, 2005; Centers for Disease Control and Prevention, 2007). Correlates and psychosocial determinants of physical activity have been investigated extensively (Hausenblas & Carron, 1997; Hagger, Chat- 1 Address correspondence to Gaston Godin, Ph.D., Canada Research Chair on Behaviour and Health, FSI-Vandry, 3rd Floor, Laval University, Quebec, Canada G1V 0A6 or (gaston. godin@fsi.ulaval.ca). DOI /PR ISSN

2 148 G. GODIN, ET AL. zisarantis, & Biddle, 2002; Trost, Owen, Bauman, Sallis, & Brown, 2002; Downs & Hausenblas, 2005). Among these, intention, a measure of motivation to adopt a behaviour (Ajzen, 1991), has been one of the strongest predictors of physical activity, explaining 21 to 26% of the variance in physical activity behaviour (Hausenblas & Carron, 1997; Hagger, et al., 2002; Downs & Hausenblas, 2005). However, this proportion of explained variance also highlights a gap between intention and behaviour; individuals with strong intentions do not always translate their intentions into action. Recently, among six prospective data sets of physical activity, Godin and Conner (2008) observed that 54.5% of participants having a positive intention to exercise had not acted at follow-up, whereas participants with a negative intention were congruent in their intention not to act. This observation agrees with Sheeran s statement (2002) that the disconnect between intention and behaviour is due mainly to people having good intentions but not acting on them; these individuals are identified as inclined abstainers. It is important to resolve how individuals with positive intentions can translate their motivation into action. One of the strategies suggested by Gollwitzer (1999) to help people act on their intentions or get started is the use of implementation intentions. Implementation Intentions Implementation intentions refer to a postintentional process of selfregulating a behaviour. This strategy includes planning attainment of goal intentions through more detailed instructions specifying when, where, and how the actions are to be performed (Gollwitzer, 1999). Individuals who fulfill this instruction are more likely to initiate action and overcome disruptive contextual influences. In the scientific literature, there are consistent reports of the positiv various health-related behaviours (Sheeran, 2002; Gollwitzer & Sheeran, 2006a). Thus, formulation of a specific plan seems to be a promising way to translate intention into action. However, such a positiv been reported consistently for physical activity behaviour. For instance, Milne, Orbell, and Sheeran (2002) showed that the combination of a motivational and volitional (i.e., of implementation intentions) intervention significantly increased the amount of physical activity among undergraduate students. Signifi rventions using implementation intentions were also observed in a few other studies that assessed behaviour over very short follow-up periods (Lippke, Ziegelmann, & Schwarzer, 2004; Sniehotta, Scholz, & Schwarzer, 2006; Ziegelmann, Lippke, & Schwarzer, 2006; Kwak, Kremers, van Baak, & Brug, 2007). In contrast, some studies did not provide clear support for tion intentions on physical activity behaviour (Prestwich, Lawton, & Con-

3 IMPLEMENTATION INTENTIONS, INTENTION STABILITY 149 ner, 2003; Arbour & Martin Ginis, 2004; Luszczynska, 2006; Hill, Abraham, & Wright, 2007; Arbour & Martin Ginis, 2009; De Vet, Oenema, Sheeran, & Brug, 2009). Even more surprising, Budden and Sagarin (2007) observed a negativ rvention technique. These inconsistent results also contrast with previous meta-analyses suggesting that implementation intentions have a medium to larg size (d = 0.65) on behaviour (Sheeran, 2002; Gollwitzer & Sheeran, 2006b). Explanations for the discrepancy observed in results include the nature of the behaviour studied, the population, methodological aspects [e.g., a high initial amount of physical activity (ceiling )], or the presence of potential moderator. In this regard, the knowledge of when implementation intentions facilitate behavioural performance (i.e., moderation analysis) remains an important question to answer to clarify under which conditions implementation intentions ar ve. One of the major moderators of the implementation been previously identified is the strength of goal intention, that is, implementation intentions are mor ve when participants have strong intentions (Norman & Conner, 2005; Sheeran, Webb, & Gollwitzer, 2005; Wiedemann, Schuz, Sniehotta, Scholz, & Schwarzer, 2009). In the scientific literature, intention stability has been consistently reported as a moderator of the relationship between intention and behaviour; the discrepancy between the intention and behaviour is reduced among individuals who have stable intention (Sheeran, 2002; Conner & Godin, 2007). This concept of stable intention is defined as the extent to which an intention remains stable over time, regardless of new information or barriers (Sheeran, Orbell, & Trafimow, 1999; Conner & Godin, 2007) and could be expressed as having strong intention (Sheeran, et al., 1999). However, it appears that the moderating bility on the efficacy of interventions aimed at changing behaviour has yet to be investigated. Considering that stable intenders are more consistent in their intention, and consequently should be either active already (i.e., positive intenders) or sedentary (i.e., negative intenders), it may be hypothesized that an intervention using implementation intentions is less likely to influence these individuals compared to unstable, but positive, intenders. The present aim was to explor tions on physical activity behaviour change, taking into account intention stability. It was ex rvention would be moderated by intention stability. Thus, individuals having a positive stable intention to exercise would not b by the intervention because these individuals should already be more active, whereas the opposite would characterize those having a positive, but unstable, intention.

4 150 G. GODIN, ET AL. Method Participants and Sampling Procedure The participants of this study were involved in a larger 6-mo. longitudinal research on genetic susceptibility to obesity. The criterion of inclusion was age between 18 and 55 years. Volunteers responded to public advertising in local media between May 2004 and March Also, students and employees of the local university and hospital and government employees were recruited by . All participants signed the consent form, and the study was approved by the Ethics Committee of the local university and in line with ethical standards of the American Psychological Association. Characteristics of the sample are presented in Table 1. According to the World Health Organization definition of overweight and obesity, 35.0% of the participants were of normal weight, 33.0% were overweight, and 32.1% were obese (World Health Organization, 2000). Student t tests Variable TABLE 1 Means and Standard Deviations of Variables at Baseline (T 0 ) and Preintervention (T 1 ) by Condition Total Sample Control Group Experimental Group M SD M SD M SD Age BMI Intention, T Intention, T Physical activity level, T Physical activity level, T n % n % n % Sex Male* Female* Education level Primary/secondary* Collegial* University* Annual income < 20, ,000 39, , Intention stability, T 1 Stable Unstable *p >.05 for all these variables. These scores were computed among the 307 participants who did not drop out between the baseline and preintervention measurement. Information from participants who dropped out was unavailable, since they did not return their T 1 questionnaire. t p

5 IMPLEMENTATION INTENTIONS, INTENTION STABILITY 151 and chi-squared analyses revealed that the two gr r significantly on any of the measures assessed at any of the measurement times (i.e., past behaviour, intention, intention stability scores, or demographic variables). Also, both groups comprised an equivalent proportion of stable and unstable individuals [χ 2 (N = 307) = 0.10, p =.75]. Research Design In the experimental design, at baseline (T 0 ), all participants attended an appointment at the local university where they completed a series of laboratory tests, including a psychosocial questionnaire on the determinants of physical activity (e.g., level of intention, perceived behavioural control, past behaviour, etc.). This questionnaire was developed based on Ajzen s recommendations (1991) and was pilot tested. The internal consistency and the temporal stability of the constructs were acceptable (Amireault, Godin, Vohl, & Perusse, 2008). Each participant received Cdn $25 at the end of their visits to cover their expenses for attending the baseline assessment session. Thereafter, they were assigned alternatively to the intervention (for implementation intentions) or the control group. Participants were aware of the two possibilities, but were not informed of the group to which they were assigned. Intervention The intervention was mail-delivered and self-administered by means of a questionnaire three months (T 1 ) after the baseline assessment session. In this self-administered questionnaire, participants in the intervention group were asked to formulate a plan by answering four questions: (1) What leisure-time physical activity/activities are you planning to do regularly during the next three months? (2) Where do you plan to practice the activity or activities regularly? (3) On what day(s) of the week do you plan to practice the physical activity or activities? and (4) At what time of day do you plan to practice the physical activity or activities? Then, participants were instructed to return their questionnaires to the investigators. No feedback was given to the participants and no more contact was made with the participants until the last follow-up at six months (T 2 ). The control group received the same questionnaire assessing only intention and behaviour, but did not receive action plan instructions. Measures Behavioural Measurement. Leisure-time physical activity was assessed at three measurement times (i.e., T 0, T 1, and T 2 ) using the following question: Within the last three months, how often did you participate in one or more physical activities of moderate intensity, totalling at least 30 minutes in the same day during your leisure time? Responses

6 152 G. GODIN, ET AL. were reported on a 7-point scale, 1: Not at all, 2: About once a month, 3: About two or three times a month, 4: About once a week, 5: About twice a week, 6: About three times a week, and 7: Four or more times a week. This question had been validated and tested previously by Gionet and Godin (1989) and Godin, Jobin, and Bouillon (1986) against VO 2 max and indices of physical fitness. Results from these studies showed acceptable validity (.22 r.40) and test-retest reliability (r =.64). Behaviour assessed at T 2 was the outcome measurement, whereas behaviour assessed at T 1 was the measurement of past behaviour. Intention stability. The score of intention stability was obtained by computing the ab rence between the mean scores on intention at T 1 and T 0 as recommended by Conner, Sheeran, Norman, and Armitage (2000). The intention construct was assessed by three items formulated as follows: (1) I intend, (2) I plan, (3) I will try... to participate regularly in one or more physical activities during the next 3 months. These items were rated on 5-point scales anchored by 1: Unlikely and 5: Likely. The mean of the sum of these three items was the Intention score, for which Cronbach coefficient alpha was.81 (Cronbach, 1951). Intention stability was operationalized as a dichotomous variable; scores with an ab rence of zero were classified as having a Stable intention, whereas the others were classified as Unstable (scores of Unstable intenders varied from 0.33 to 3.67). Results Descriptive Results The mean Intention scores at T 0 and T 1 were very high, indicating that participants had a positive predisposition toward regular physical activity. As expected, at T 1 Stable intenders were more active (5.94 ± 1.26) than Unstable intenders (M = 4.75, SD = 1.66; t = 7.01, p = 0.2e-13). A majority (56.4%) of the sample reported practicing moderate leisure-time physical activity for almost 30 min. and at least three times a week at T 1. A total of 349 individuals were assigned randomly to either the control or the intervention group (see Fig. 1). Of these, 307 completed the questionnaire at T 1. Finally, 221 participants completed the study at T 2 and their data were included in the analysis. The overall attrition rate was 36.7%. Participants who dropped out between the baseline and T 1 had a significantly higher body mass index than participants who completed the T 1 questionnaire (i.e., M = 30.3, SD = 6.6 vs M = 27.6, SD = 5.9; t = 2.69, p =.008, d = 0.43) and were more likely to be men [χ 2 (N = 349) = 7.09, p =.008]. However, par r significantly on all other variables (including Intention Stability), from those who dropped out at follow-up. SAS Version 9.1 software was used for all statistical analyses (SAS Institute, Inc., Cary, NC).

7 IMPLEMENTATION INTENTIONS, INTENTION STABILITY 153 N Fig. 1. Participant selection Effect of Implementation Intentions on Behavioural Change An analysis of covariance with past behaviour (T 1 ) as the covariate r condition (F = 0.33, p =.57); the physical activity rating in the intervention group was M = 5.59 (SD = 1.49) compared to M = 5.38 (SD = 1.67) in the control group. However, signifi past behaviour (F = , p = ; η 2 = 0.40) and Intention Stability (F = 5.16, p =.02; η 2 = 0.02) were noted, as well as a significant interaction between Intention Stability and condition (F = 4.26, p =.04; η 2 = 0.02). 2 This inter rated in Fig The moderating bility was also verified according rent definitions of this concept [see Conner, et al. (2000) for more information]. As a continuous variable the moderating bility on implementation intentions remains significant (F = 4.10, p =.04). Similarly, significant interactions were observed when intention stability was operationalized either rences of each item (F = 7.14, p =.008) or as the number of items changing (F = 5.21, p =.024).

8 154 G. GODIN, ET AL. 7 Physical Activity * 1 0 Stable Intenders Unstable Intenders Fig. 2. rvention on physical activity at T 2, controlling for baseline values. *p =.05 between conditions. Control ( ); Experimental ( ). Results from post hoc comparisons indicated that the Unstable intenders in the intervention group (M = 5.48, SE =.17) were significantly more active (F = 3.85, p =.05) than the Unstable intenders in the control group (M = 5.03, SE =.17) at T 2. Among the Stable intenders, rence was observed between participants in the control (M = 5.73, SE =.15) and the intervention (M = 5.54, SE =.15; F = 0.83, p =.36) groups. The over size of the intervention was small (d =.13), but more precisely, it was small among Stable intenders (d =.11), and medium (d =.39) among Unstable intenders (Cohen, 1988). Discussion This study ev rvention using implementation intentions designed to increase the amount of physical activity among a sample of adults aged between 18 to 55 years. Overall, the analysis showed that the intervention did not increase their frequency of physical activity. However, intention stability ratings moderated the efficacy of an intervention using implementation intentions. Consequently, the interv ve, but only among Unstable intenders. As expected, the frequency of physical activity at baseline was higher among Stable than Unstable intenders; this finding is congruent with recent observations reported by Conner and Godin (2007) for several healthrelated behaviours. The present result also suggests that any intervention aimed at Stable intenders is likely to be limited by some kind of ceiling ef-

9 IMPLEMENTATION INTENTIONS, INTENTION STABILITY 155 fect, given their high behaviour at baseline. As such, it can be suggested that Stable intenders do not represent an appropriate target group for interventions using implementation intentions. Indeed, Stable negative intenders will probably remain sedentary, 3 since this kind of intervention is known to b ve only for individuals having a positive intention, whereas Stable positive intenders will continue to exercise as before, regardless of the intervention. Consequently, no change in behaviour should be observed. On the other hand, Conner and Godin (2007) suggest that interventions could be used to increase intention stability and consequently promote health-related behaviours amongst those with positive intentions to perform these behaviours. According to Gollwitzer (1999), the formulation of a plan facilitates stabilization of an individual s intention regarding a behaviour, as indicated by the agreement of the unstable intenders being positiv by the implementation intentions intervention. 4 However, because no postintervention measurement of temporal stability was obtained, the present findings make it impossible to ascer of the intervention was a result of change in intention stability. This may be an interesting question to investigate. There are a number of published studies providing evidence that strong supporting intentions are needed for implementation intentions to b ve (Koestner, Lekes, Powers, & Chicoine, 2002; Sheeran, et al., 2005). However, other researchers have observed that implementation intentions are mor ve among those who experience volitional difficulties (Brandstatter, Lengfelder, & Gollwitzer, 2001). Thus, based on the findings of these latter authors, this could be one of the reasons why the re stronger among people with unstable compared to stable intentions. 5 The present findings also have implications for the evaluation of interventions aimed at changing behaviour. Given that stability of intention moderates the efficacy of an implementation intentions intervention, it is also possible that stability of intention moder kind of educational intervention aimed at changing behaviour. Thus, in future studies, rts should be directed at recruiting individuals with 3 In the present study, all Stable intenders had positive intentions. 4 Among Unstable intenders, only three participants had negative intentions at both preintervention and baseline measurements. When these three individuals were excluded from the analysis, the interaction between intention stability and condition remained significant (F = 3.81, p =.05). 5 In support for this interpretation, the Stable and Unstable intenders of both groups in the pr red significantly on perceived behavioural control assessed at baseline (t = 7.63, p <.0001); Unstable intenders had a lower perception of control. Nonetheless, controlling for rceived behavioural control in the analysis did not modify the results: the intervention remained significantly moderated by stability of intention (F = 5.08, p =.03).

10 156 G. GODIN, ET AL. positive, but unstable, intentions. One strategy could be to select individuals who intend to exercise but who are still sedentary or do not meet the recommended level of physical activity for health benefits. In past evaluative research, the stab ve undermined veness of numerous interventions with small or nonsignificant observed average behavioural changes. Consequently, future research should investigate the potential moderating veral factors that could be responsible for the nonsignifi given intervention. This also highlights the fact that public health planners should have better knowledge of the populations for whom interventions are developed. Certain limitations must be mentioned. First, this study was completed among a sample of volunteers. This group was likely more motivated toward physical activity than one would expect from the general population, as suggested by the mean intention and physical activity ratings among this group at baseline. Therefore, it is possible that a larger group of more sedentary but motivated individuals exposed to the same intervention would have r r r the intervention. However, the high physical activity at baseline in this sample can be seen as a positive asset, because it made it more difficult to confirm the moderating role of stability of intention. Secondly, although a validated measure was used, it was a self-report. This could lead to difficulties in detecting small variations in behaviour because of measurement error. However, if there was bias in self-reporting, there is no reason to believ the experimental and control gr rently. In addition, the present study assumes that those with Stable intentions at baseline and at the time of delivery of the intervention remained Stable between these two measurement times (and Unstable intentions between these two measurement times remained Unstable). This may have influenced the classification of individuals as having Stable or Unstable intentions at the time of group allocation. Future studies could adopt other measures of stability based on multiple time measurements. Finally, the participants formed a group of well-educated individuals, and caution should be exercised before generalizing about the present findings. Additional studies are required before a definite conclusion can be reached on the moderating stab vity behaviour. REFERENCES Ajzen, I. (1991) The theory of planned behavior. Organizational Behavior and Human Decision Processes, 50, Amireault, S., Godin, G., Vohl, M. C., & Perusse, L. (2008) Moderators of the intention-behaviour and perceived behavioural control-behaviour relationships for leisure-time physical activity. The International Journal of Behavioral Nutrition and Physical Activity, 5, 7.

11 IMPLEMENTATION INTENTIONS, INTENTION STABILITY 157 Arbour, K. P., & Martin Ginis, K. A. (2004) Helping middle-aged women translate physical activity intentions into action: combining the theory of planned behavior and implementation intentions. Journal of Applied Biobehavioral Research, 9, Arbour, K. P., & Martin Ginis, K. A. (2009) A randomised controlled trial of the effects of implementation intentions on women s walking behaviour. Psychology & Health, 24, Brandstatter, V., Lengfelder, A., & Gollwitzer, P. M. (2001) Implementation intentions and efficient action initiation. Journal of Personality and Social Psychology, 81, Budden, J. S., & Sagarin, B. J. (2007) Implementation intentions, occupational stress, and the exercise intention-behavior relationship. Journal of Occupational Health Psychology, 12, Cameron, C., Craig, C. L., & Paolin, S. (2005) Local opportunities for physical activity and sport: trends from Ottawa, Canada: Canadian Fitness and Lifestyle Research Institute. Centers For Disease Control and Prevention. (2007) Prevalence of regular physical activity among adults: United States, 2001 and Morbidity and Mortality Weekly Report, 56, Cohen, J. (1988) Statistical power analysis for the behavioral sciences. (2nd ed.) Hillsdale, NJ: Erlbaum. Conner, M., & Godin, G. (2007) Temporal stability of behavioural intention as a moderator of intention-health behaviour relationships. Psychology & Health, 22, Conner, M., Sheeran, P., Norman, P., & Armitage, C. J. (2000) Temporal stability as a moderator of relationships in the Theory of Planned Behaviour. British Journal of Social Psychology, 39, Cronbach, L. J. (1951) Coefficient alpha and the internal structure of tests. Psychometrika, 16, De Vet, E., Oenema, A., Sheeran, P., & Brug, J. (2009) Should implementation intentions interventions be implemented in obesity prevention: the impact of if-then plans on daily physical activity in Dutch adults. The International Journal of Behavioral Nutrition and Physical Activity, 6, 11. Downs, D. S., & Hausenblas, H. A. (2005) The theories of reasoned action and planned behavior applied to exercise: a meta-analytic update. Journal of Physical Activity and Health, 2, Gionet, N. J., & Godin, G. (1989) Self-reported exercise behavior of employees: a validity study. Journal of Occupational Medicine, 31, Godin, G., & Conner, M. (2008) Intention-behavior relationship based on epidemiologic indices: an application to physical activity. American Journal of Health Promotion, 22, Godin, G., Jobin, J., & Bouillon, J. (1986) Assessment of leisure time exercise behavior by self-report: a concurrent validity study. Canadian Journal of Public Health, 77, Gollwitzer, P. M. (1999) Implementation intentions, strong. American Psychologist, 54, Gollwitzer, P. M., & Sheeran, P. (2006b) Implementation intentions and goal achievement: rocesses. In P. Z. Mark (Ed.), Advances in experimental social psychology. Vol. 38. Waterloo, Ontario, Canada: Academic Press. Pp

12 158 G. GODIN, ET AL. Hagger, M. S., Chatzisarantis, N. L. D., & Biddle, S. J. H. (2002) A meta-analytic review of the theories of reasoned action and planned behavior in physical activity: predictive validity and the contribution of additional variables. Journal of Sport and Exercise Psychology, 24, Hausenblas, H. A., & Carron, A. V. (1997) Application of the theories of reasoned action and planned behavior to exercise behavior: a meta-analysis. Journal of Sport & Exercise Psychology, 19, Hill, C., Abraham, C., & Wright, D. B. (2007) Can theory-based messages in combination with cognitive prompts promote exercise in classroom settings? Social Science & Medicine, 65, Koestner, R., Lekes, N., Powers, T. A., & Chicoine, E. (2002) Attaining personal goals: self-concordance plus implementation intentions equals success. Journal of Personality and Social Psychology, 83, Kwak, L., Kremers, S. P., van Baak, M. A., & Brug, J. (2007) Formation of implementation intentions promotes stair use. American Journal of Preventive Medicine, 32, Lippke, S., Ziegelmann, J. P., & Schwarzer, R. (2004) Initiation and maintenance of physical exercise: stage-specifi g intervention. Research in Sports Medicine, 12, Luszczynska, A. (2006) An implementation intentions intervention, the use of a planning strategy, and physical activity after myocardial infarction. Social Science & Medicine, 62, Milne, S., Orbell, S., & Sheeran, P. (2002) Combining motivational and volitional interventions to promote exercise participation: protection motivation theory and implementation intentions. British Journal of Health Psychology, 7, Norman, P., & Conner, M. (2005) The theory of planned behavior and exercise: evidence for the mediating and moderating roles of planning on intention-behavior relationships. Journal of Sport & Exercise Psychology, 27, Prestwich, A., Lawton, R., & Conner, M. (2003) The use of implementation intentions and the decision balance sheet in promoting exercise behaviour. Psychology & Health, 18, Sheeran, P. (2002) Intention-behavior relations: a conceptual and empirical review. European Review of Social Psychology, 12, Sheeran, P., Orbell, S., & Trafimow, D. (1999) Does the temporal stability of behavioral intentions moderate intention-behavior and past behavior future behavior relations? Personality and Social Psychology Bulletin, 25, Sheeran, P., Webb, T. L., & Gollwitzer, P. M. (2005) The interplay between goal intentions and implementation intentions. Personality and Social Psychology Bulletin, 31, Sniehotta, F. F., Scholz, U., & Schwarzer, R. (2006) Action plans and coping plans for physical exercise: a longitudinal intervention study in cardiac rehabilitation. British Journal of Health Psychology, 11, Trost, S. G., Owen, N., Bauman, A. E., Sallis, J. F., & Brown, W. (2002) Correlates of adults participation in physical activity: review and update. Medicine & Science in Sports & Exercise, 34, Warburton, D. E., Katzmarzyk, P. T., Rhodes, R. E., & Shepard, R. J. (2007) Evidenceinformed physical activity guidelines for Canadian adults. Applied Physiology, Nutrition, and Metabolism, 32, S16-S68.

13 IMPLEMENTATION INTENTIONS, INTENTION STABILITY 159 Warburton, D. E., Nicol, C. W., & Bredin, S. S. (2006) Health benefits of physical activity: the evidence. Canadian Medical Association Journal, 174, Wiedemann, A. U., Schuz, B., Sniehotta, F., Scholz, U., & Schwarzer, R. (2009) Disentangling the relation between intentions, planning, and behaviour: a moderated mediation analysis. Psychology & Health, 24, World Health Organization. (2000) Obesity: preventing and managing the global epidemic: report of a WHO consultation. Geneva, Switzerland: Author. Ziegelmann, J. P., Lippke, S., & Schwarzer, R. (2006) Adoption and maintenance of physical activity: planning interventions in young, middle-aged, and older adults. Psychology & Health, 21, Accepted February 4, 2010.