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

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.