Promoting physical activity among youth: strategic places in the classroom

This study aims to increase physical activity through real-life social network intervention among youth between 12 and 15 years old. The research uses smartphones to set out questionnaires and the intervention itself. Physical activity is measured by accelerometer (Fitbit flex). In the intervention groups, influence agents are assigned based on peer nomination. The influence agents will have the task to promote physical activity among their classmates. Therefore the influence agents receive information on the research phone and strategies how they can promote physical activity among their classmates. Influence agents will be based on three different selection criteria (the three different intervention groups): degree centrality, betweenness centrality and closeness centrality.

Hypothesis 1: a social network intervention is more effective in increasing physical activity in youngsters compared to a control condition.

the intervention will exist out of two weeks. The first week (mid November) is the baseline measure. Participants will wear the accelerometer for seven consecutive days. After a month, participants will wear the accelerometer again for seven consecutive days (the intervention week; mid December).

The social network intervention will make use of the social network by selecting influence agents based on peer nominations. Participants will rate classmates on friendship, communication about physical activity, impression management, and with whom they spend time. Based on these nominations, a social network will be modeled. Classrooms will be randomly assigned to one out of three intervention conditions or the control condition. In the intervention conditions the groups will exist out of influence agents who are based on: (1) degree centrality, (2) betweenness centrality, or (3) closeness centrality. The influence agents will be approached and trained via the research application. They will receive useful information about physical activity as well as strategies to induce physical activity in others. The control condition will have no influence agents. Therefore, no participants in the control condition will receive information nor strategies.