Table 1.

Concepts, number of items, and example question of the child questionnaire

Concept	N items	Items
Demographics	12	Name of school, grade (4th, 5th, 6th), birth month, birth year, gender, home address, country of birth, country of birth parents, number of siblings
PA on a school day	6	Television viewing, transportation to school and from school (walking, cycling, by step/waveboard/skateboard/skates, driven by scooter, driven by car, driven by bus, other), longest performed activity during recess (running, jumping, playing, walking, sitting and chatting, standing and chatting, playing inside, other), activity after school time yesterday (playing outside, sports, active play inside, low intensity play inside, swimming, music or drama lesson, PC/tablet/smartphone use, watching television)
Sports participation	1	Member of sports clubs (no, soccer, tennis, dancing, gymnastics/ballet, swimming, horse riding, martial art, basketball, volleyball, handball, hockey, badminton, athletics, cycling, table tennis, korfball, scouts, afterschool PA, other)
Nutrition intake on a school day [77]	12	Breakfast intake, fruit intake and vegetable intake at school (yes/no), amount of fruit intake (0.5, 1, 2, 3 or more pieces), water consumption at school yesterday (yes/no), sugar-sweetened beverages (yes/no), milk drinks (yes/no), energy drinks (yes/no), and sports drinks consumption at school (yes/no), candy (yes/no), cookie (yes/no), and snack consumption (yes/no)
PA enjoyment [78]	16	Example: When I am physically active… I enjoy it. (5-point Likert scale: 1 = totally disagree, 4 = totally agree, 5 = don’t know)
Food and drink preferences [79]	16	Examples: Which of the following foods do you prefer more? (fruit or savory snacks) / Which of the following drinks do you prefer more? (soft drink or fruit juice)
PA preferences [79]	28	Example: Which of the following physical activities do you prefer more? (cycling or watching television)