Participants
RECRUITMENT, RECRUITMENT
To estimate the required sample size to test the study hypotheses, power calculation was conducted using G*Power Version 3.1.9.7 [We managed to recruit a total sample size of 68 children (28 boys, 40 girls) and one parent for each child who participated in the study. Students’ ages ranged from 11 to 15 years (Participant flow diagram in the pilot studyEligible participants were students without restrictions on their participation in PE classes and their parents. Recruitment was school based, and participants were cluster-randomized by school. Invitation letters were sent to randomly selected schools in Tartumaa County, Estonia. After confirmation, the researchers visited the classes 6–7 in consenting schools in person, introduced the study and distributed informed consent forms for students and parents. After a week, the filled-out consent forms were collected from schools, resulting in recruitment of student and parent pairs to participate in the study. The intervention was carried out during 2021/22 school year.