What Friends Are for: Comparing the Effectiveness of an Individual Planning Intervention With Collaborative Planning

The physiological and psychological benefits of regular physical activity (PA) and reduced sedentary behavior are well documented. Nevertheless, the majority of adolescents in western countries, e.g., Switzerland, do not meet the recommendations for moderate to vigorous PA of at least one hour per day. However, changing PA seems to be a major challenge even for individuals with good intentions to do so. This phenomenon is the so called intention-behavior gap. Planning interventions have been proposed as an effective way of translating intentions into action. Planning includes action planning (i.e., individual creation of plans when, where and how to engage in a behavior change) and coping planning (i.e., what an individual will do in case barriers arise). So far, good evidence has been found for individual planning increasing PA among adults. Such research with adolescents, however, is in its early stages. Moreover, recent research suggests that an individual's behavior change is also dependent on members of the social network. Consequently, the idea of conjoint planning was introduced recently. Conjoint planning comprises two planning formats, namely collaborative and dyadic planning. Dyadic planning implies creating plans together with a partner, but executing the behavior individually. In contrast, collaborative planning is defined as conjoint planning of at least two individuals when, where and how to perform a behavior together. An example would be "If we go shopping, we will take the bicycles to get there". It is assumed that conjoint planning stimulates social exchange processes between the planning partners. Social exchange processes are interactions between individuals that influence an individual's behavior, emotions, and cognitions and have been shown to play a significant role for health behavior change. A central component of social exchange processes is social support. Regarding PA in adolescents, the influence of peers and friends become increasingly important due to increased autonomy in adolescence. However, past research on health behavior change in adolescents has not yet examined effects of conjoint planning to enhance PA in adolescents. Although a few studies showed promising effects of conjoint planning in adults and adolescents, some important questions still remain open, which will be addressed in this project focusing on individual and collaborative planning. Our research questions and hypotheses are the following:

Research question 1: Is planning an effective strategy to promote PA in adolescents when using daily based measures of PA and long-term follow-ups?

Hypothesis 1.1. Adolescents, who take part in one of the two planning interventions, will show higher levels of (self-reported/objectively measured) PA compared to the control groups when comparing PA on a daily basis, one week (directly after the intervention), one month (after the booster session) and six months after the intervention.

Hypothesis 1.2. Adolescents in the individual and collaborative planning intervention will report higher PA one month and six months after the intervention compared to the control groups.

Research question 2: Do collaborative and individual planning differ regarding their effectiveness to promote PA in adolescents?