Elsevier

Preventive Medicine

Volume 53, Issue 3, 1 September 2011, Pages 182-187
Preventive Medicine

Intervention effects of exercise self-regulation on physical exercise and eating fruits and vegetables: A longitudinal study in orthopedic and cardiac rehabilitation

https://doi.org/10.1016/j.ypmed.2011.06.019Get rights and content

Abstract

Objective

The primary objective of this study was to unveil the mechanisms by which an exercise self-regulation intervention affects physical exercise in a rehabilitation context. The second aim was to investigate whether the intervention led to changes in fruit and vegetable intake that was not targeted in the intervention. Finally, it was tested whether changes in exercise habit strength may explain such a transfer effect.

Method

A quasi-experimental design was conducted in Germany between 2009 and 2011 with 725 rehabilitation patients. Patients received either a self-regulation intervention or an online questionnaire. Six weeks after discharge, self-reported changes in exercise and dietary behaviors, exercise habit strength, and cognitions were measured.

Quantitative results

The exercise self-regulation intervention led to a higher increment in exercise behavior, exercise habit strength, and fruit and vegetable intake than the control condition. Changes in physical exercise were mediated by changes in action control (slope = 0.04; 99% CI = 0.01 to 0.06) and satisfaction (slope = 0.05; 99% CI: = 0.02 to 0.08), but not in action planning. Changes in fruit and vegetable intake were mediated by changes in exercise habit strength (slope = 0.05; 99% CI = 0.01 to 0.08).

Conclusion

Interventions could be optimized if they aim at fostering exercise habits. This in turn may also facilitate transfer effects from one health behavior to the other.

Highlights

► We investigate the intervention effects of exercise self-regulation on exercise. ► We examine whether the exercise intervention also promotes healthy nutrition. ► We test whether such a transfer effect is explained by changes in exercise habit. ► Focusing on exercise self-regulation promotes exercise behavior in rehabilitation. ► Intervention effects on exercise may transfer to healthy nutrition.

Introduction

Individuals can prevent and manage existing diseases, such as cardiovascular diseases and orthopedic disorders, by adopting a healthy diet (Brunner et al., 2008, Chahoud et al., 2004) and regular exercise (Conn et al., 2008, Dalal et al., 2010, Resnick et al., 2007). Adhering to multiple health behavior recommendations, however, is a difficult self-regulatory task for many patients in medical rehabilitation. Despite good intentions, many patients fail to initiate and maintain a healthy diet (e.g., Luszczynska and Cieslak, 2009) and regular exercise (e.g., Reuter et al., 2009) after discharge from the rehabilitation program. Thus, there is a need to develop theory-based interventions for clinical practice and identify those psychological processes that initiate and maintain multiple health behaviors.

As proposed by the Health Action Process Approach (HAPA; Schwarzer, 2008) and Rothman's Framework of Health Behavior Change (Rothman, 2000, Rothman et al., 2004), decisions regarding exercise changes and maintenance are predicted to rely on self-regulatory variables, such as action planning (Lippke et al., 2004, Reuter et al., 2009, Wiedemann et al., 2011, Ziegelmann et al., 2007), action control (Pomp et al., 2010, Sniehotta et al., 2005a, Sniehotta et al., 2006), as well as perceived satisfaction with experienced behavior outcomes (Fleig et al., 2011). Action planning refers to a prospective self-regulatory strategy, by which people mentally link behavioral responses to specific situations to achieve certain goals (Sheeran and Orbell, 1999, Sniehotta et al., 2005b). Action control refers to an in situ strategy including the investment of self-regulatory effort, awareness of one's own standards, as well as self-monitoring behavior (Sniehotta et al., 2005b, Sniehotta et al., 2006).

There is convincing evidence that psychological interventions in rehabilitation are effective in improving patients' post-rehab exercise behavior by increased action planning (Luszczynska, 2006, Ziegelmann et al., 2006) and action control (Sniehotta et al., 2005b).

Whereas mechanisms of changes in single health behaviors have been extensively studied, there has been only little theory-guided research on the processes of multiple health behavior change (Prochaska et al., 2008). The present study investigates the mechanisms by which an exercise self-regulation intervention affects (a) exercise behavior and (b) fruit and vegetable intake in a sample of rehabilitation patients.

Psychological interventions in secondary prevention often focus on the promotion of selected health behaviors (e.g., physical exercise only; Fuchs et al., in press). From a multiple health behavior perspective, the question emerges, whether interventions targeted to change one health behavior may also initiate changes in other behaviors (Lippke et al., in press, Prochaska and Sallis, 2004, Wilcox et al., 2000). For example, an intervention targeted at physical exercise may also have a positive effect on healthy nutrition. Such an effect may be referred to as a “transfer effect”, as positive intervention effects on one behavior are also observed in another behavior (Lippke et al., in press). Transfer effects may take two different forms depending on the time sequence of behavior changes. First, changes in the target behavior of an intervention and the non-target behavior can occur simultaneously (i.e., transfer as co-occurrence). Second, changes in the target behavior and non-target behavior may occur sequentially. In other words, changes in the target behavior initiate subsequent changes in the non-target behavior (i.e., transfer as carry-over).

Empirical support for the occurrence of transfer effects in intervention studies has been inconsistent. An intervention study by Mata et al. (2009) revealed that a psychological intervention primarily targeted at physical exercise not only increased exercise behavior but was also associated with improved eating regulation. Similarly, Dutton et al. (2008) revealed that changes in physical exercise due to an exercise self-regulation intervention covaried with reductions in fat intake. On the contrary, concurrent effects of the intervention on fruit and vegetable intake as well as subsequent effects of the intervention on changes in fat intake and fruit and vegetable intake could not be found (Dutton et al., 2008). Other studies also failed to show that exercise-only interventions facilitate changes in fruit and vegetable intake (Prochaska and Sallis, 2004, Wilcox et al., 2000) and other indicators of healthy eating (Prochaska and Sallis, 2004).

According to the Strength and Energy Model (Baumeister et al., 2000), self-regulation is a limited resource which may be utilized across different domains of actions or health behaviors (Hagger et al., 2010). Theoretically, mechanisms of transfer effects have been attributed to a transfer of self-regulatory resources from one behavior to the other (Lippke et al., in press, Nigg et al., 2009). For example, changes in physical exercise may also promote self-monitoring of one's nutrition behavior or the generation of nutrition-specific action plans.

As a health behavior becomes more routinized, less self-regulatory effort is required for its execution (Aarts et al., 1997, Baumeister et al., 2000, Orbell and Verplanken, 2010, Verplanken and Melkevik, 2008). In orthopedic rehabilitation patients, Ziegelmann et al. (2007) revealed that exercise engagement becomes less dependent on self-regulation after an individual had integrated exercise into his or her lifestyle. Thus, if an intervention promotes habituation in one health behavior, more self-regulatory resources may be available for another behavior. In other words, as individuals move further along the behavior change process in a single behavior, transfer of resources to another health behavior may become more likely. Analyzing the co-variation of changes in exercise habit and changes in healthy nutrition behavior may be a first step to investigate this “facilitation hypotheses”.

The present study investigates the psychological mechanisms through which an exercise self-regulation intervention promotes (a) physical exercise and (b) fruit and vegetable consumption. First, the following hypotheses on primary intervention outcomes and working mechanisms were tested: (a) the intervention leads to an increase in physical exercise compared to a control condition, (b) the intervention increases action planning, action control, and satisfaction, and (c) changes in action planning, action control, and satisfaction mediate between the exposure to the experimental conditions and changes in physical exercise. Next, hypotheses on transfer effects and working mechanisms were tested: (d) the intervention leads to an increase in fruit and vegetable intake (i.e., transfer effect), (e) the intervention increases exercise habit strength, and (f) changes in exercise habit strength explain the increase in fruit and vegetable intake.

Section snippets

Participants and procedure

Patients with a medical indication to engage in regular exercise after rehabilitation were invited to participate in an exercise program during their first week of stay in two orthopedic rehabilitation centers (one in-patient and one out-patient) and one in-patient cardiac center. The exercise self-regulation intervention and the questionnaire were delivered via computers. In Germany, a stay in rehabilitation is usually covered by a compulsory insurance (i.e., German Pension Insurance). All

Dropout analyses

Results indicated that patients who continued study participation were more likely to have a partner than those who did not (p = 0.04). Besides that, no other differences were found with regard to treatment condition, physical exercise, exercise habit, fruit and vegetable intake, social-cognitive variables (i.e., action planning, action control, satisfaction), and socio-demographic variables (all p > 0.05).

Randomization check

Results revealed no baseline differences across the two conditions regarding physical

Discussion

The first purpose of the study was to examine the effects of an exercise self-regulation intervention addressing action planning, action control, and satisfaction on changes in physical exercise in rehabilitation patients. These analyses are novel in terms of considering satisfaction with exercise experiences as a mediator of intervention effects. The second aim of the study was to investigate whether and how an exercise self-regulation intervention promotes fruit and vegetable consumption. By

Conclusions

This study adds to our understanding of self-regulatory mechanisms in exercise behavior after rehabilitation. The addition of psychological interventions targeted at action control and satisfaction may increase the effectiveness of standard rehabilitation treatment. For the promotion of a healthy lifestyle, (a) psychological interventions should address behavior-specific self-regulatory variables, (b) take into account measures of habit strength, and (c) utilize transfer effects from one

Conflict of interest statement

None of the authors have any conflicting interests.

Acknowledgments

This work has been funded by the Deutsche Rentenversicherung Bund (DRV; German Pension Insurance) within the project FABA (Project ID 8011-106-31/31.91). The authors would like to thank the rehabilitation clinics and their patients for participating in this study. We especially appreciate the support of Mrs. Pimmer, Dr. Kiwus, Dr. Glatz, Dr. Milse, and Dr. Johnigk.

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