Study: NCT03575559

Intervention type: BEHAVIORAL
Group type: EXPERIMENTAL
Intervention: Individual planning
Description: Each participant forms up to three action and up to three coping plans individually, without consulting the participating friend, but discussing the plans with the experimenter. CONTENT: The planning materials and forms have the following sections: (a) information on the importance of planning (b) instructions of what should be included in a good plan (the when, where, and how components), (c) formulating action and coping plans based on the if-then structure. Action plans (referring to when, when, and how the individual will act) as well as coping plans (referring to how to overcome potential difficulties, risky situations or temptations to not engage in physical activity).

Intervention type: BEHAVIORAL
Group type: EXPERIMENTAL
Intervention: Collaborative planning
Description: Both friends together create up to three if-then plans on when, where, and how both will implement PA together. In addition, up to three coping plans will be formed together. This jointly developed plan is discussed with the experimenter. CONTENT: The planning materials and forms have the following sections: (a) information on the importance of planning (b) instructions of what should be included in a good plan (the when, where, and how components), (c) formulating action and coping plans based on the if-then structure. Action plans refers to when, when, and how the individual will act) as well as coping plans (referring to how to overcome potential difficulties, risky situations or temptations to not engage in PA). All materials are formulated using the plural.

Intervention type: BEHAVIORAL
Group type: ACTIVE_COMPARATOR
Intervention: Education and motivation treatment
Description: Adolescents will watch a movie from the Federal Office of Public Health Switzerland including the guidelines of physical activity (PA) for adolescents. All adolescents respond to a quiz afterwards. After the quiz, the experimenter repeats the guidelines for PA based on a brochure that all adolescents can take home with them. In addition, the experimenter asks for barriers and benefits of PA the adolescents perceive. Next to it, the experimenter explains that a weight gain might be possible due to PA in the beginning. Furthermore, the experimenter presents how the data of the accelerometer should look like if one is sufficiently physical active. As a last part self-efficacy as an important aspect of goal success is mentioned. The materials exclude any planning statements.

Intervention type: BEHAVIORAL
Group type: EXPERIMENTAL
Intervention: Education and motivation treatment
Description: Adolescents will watch a movie from the Federal Office of Public Health Switzerland including the guidelines of physical activity (PA) for adolescents. All adolescents respond to a quiz afterwards. After the quiz, the experimenter repeats the guidelines for PA based on a brochure that all adolescents can take home with them. In addition, the experimenter asks for barriers and benefits of PA the adolescents perceive. Next to it, the experimenter explains that a weight gain might be possible due to PA in the beginning. Furthermore, the experimenter presents how the data of the accelerometer should look like if one is sufficiently physical active. As a last part self-efficacy as an important aspect of goal success is mentioned. The materials exclude any planning statements.

Intervention type: BEHAVIORAL
Group type: ACTIVE_COMPARATOR
Intervention: Education and motivation treatment
Description: Adolescents will watch a movie from the Federal Office of Public Health Switzerland including the guidelines of physical activity (PA) for adolescents. All adolescents respond to a quiz afterwards. After the quiz, the experimenter repeats the guidelines for PA based on a brochure that all adolescents can take home with them. In addition, the experimenter asks for barriers and benefits of PA the adolescents perceive. Next to it, the experimenter explains that a weight gain might be possible due to PA in the beginning. Furthermore, the experimenter presents how the data of the accelerometer should look like if one is sufficiently physical active. As a last part self-efficacy as an important aspect of goal success is mentioned. The materials exclude any planning statements.

Intervention type: BEHAVIORAL
Group type: EXPERIMENTAL
Intervention: Education and motivation treatment
Description: Adolescents will watch a movie from the Federal Office of Public Health Switzerland including the guidelines of physical activity (PA) for adolescents. All adolescents respond to a quiz afterwards. After the quiz, the experimenter repeats the guidelines for PA based on a brochure that all adolescents can take home with them. In addition, the experimenter asks for barriers and benefits of PA the adolescents perceive. Next to it, the experimenter explains that a weight gain might be possible due to PA in the beginning. Furthermore, the experimenter presents how the data of the accelerometer should look like if one is sufficiently physical active. As a last part self-efficacy as an important aspect of goal success is mentioned. The materials exclude any planning statements.