Crystal Smit

Chapter 3 52 During all waves, participants received the MyMovez Wearable Lab for seven calendar days. The Wearable Lab consisted of a smartphone with a preinstalled research application and an activity-tracking bracelet (Bevelander et al., 2018; MyMovez, 2017). The research application served as the measurement tool for the questionnaires. Participants received daily questionnaires at random time points between 7:00 a.m. and 7:30 p.m., but not during school hours, except for school breaks. The research application included an avatar, a puzzle game (Zoko), and a social media platform. Through this social media platform, the participants could contact their peers and the researchers. The MyMovez research program was approved by the ethics committee on social sciences and ethical review board from the European Research Council (617253). Measures Fruit and Vegetable Consumption To assess fruit consumption, participants indicated on three different days (i.e., every other day during each data wave) on a 7-point scale ranging from 0 = ‘none’ to 6 = ‘six or more’, how many pieces (i.e., units) of fruit they had consumed the day before (Ocke et al., 1997). The same question was asked to assess vegetable consumption. One unit was defined as one apple or pear, or a handful of grapes, snack tomatoes, or cucumbers. A more detailed description of the food items can be found in the MyMovez protocol (Bevelander et al., 2018). Averaging the participants’ reported consumption over the three days produced a total score for fruit and vegetable consumption. Water Consumption To assess water consumption, participants indicated on three different days (i.e., every other day during each data wave) on an 8-point scale, ranging from 0 = ‘zero glasses per day’ to 7 = ‘seven or more glasses per day’, how much water they had drunk the day before (Ocke et al., 1997; Smit et al., 2016). An illustration was used to instruct the participants that “one glass” also meant one can, bottle, or package of approximately 200 ml. Averaging the participants’ reported consumption over the three days led to the total score for water consumption.