ActTeens Program: A Program to Improve the Physical Activity Level, Physical Fitness, Cardiometabolic and Mental Health in Adolescents

Introduction The practice of regular physical activity (PA) has been associated with numerous health benefits including improve cardiorespiratory fitness (CRF), body composition, cardiometabolic profile and mental health. Furthermore, evidence suggests that 81% of school-aged adolescents aged 11 to 17 years not meeting the current recommendations, and in Brazil, only 8.4% adolescents are physically active. In Brazil, school-based programs have been developed with a focus on the promotion of active behaviour in teens, however, these programs implemented interventions with strategies only in the school context with predominantly focus on the aerobic component of youth PA guidelines. In addition, a number limit of physical activity programs in the school setting is being conducted in low-and- middle-income countries. Thus, considering PA benefits for health, knowing the need to develop strategies to encourage active behavior both school and out of school, and that few studies of interventions are approach with focusing on muscular fitness (MF). There is a need to implement school-based programs that provide new opportunities for practice in the school setting and promote an active lifestyle outside of school for adolescents.

METHODS Study Design The trial is approved by human research ethics committee of the States University of Northern of Parana (nº 4.452.513). The design, conduct, and reporting will adhere to the guidelines of the Consolidated Standards of Reporting Trials. The intervention will be evaluated using a two-arm school-based randomized clinical trial with one intervention group (IG) and a control group (CG). The assessment will be conducted at baseline, 6 months (primary end).

School recruitment and selection The secondary public schools in Jacarezinho city, including students from 13 - 14 years (i.e., Grade 8 and 9) will be recruited via the list provided by the Regional Education Center of Jacarezinho city, Pr, regarding the 2022 academic year. Then emails will be sent directly to eligible schools (school principals and Grade 8 and 9 coordinators). Each school should provide a list with the number of classes, for Grade 8 and 9, one class of each year education will be randomly selected to participate.

Participants Two grades 8 and 9 (one each year) teachers per school that agree to participate in the program during the scheduled class time, and students.

Sample size calculation The sample size estimation was conducted using G*Power (version 3.1) and based on detecting changes in the primary outcome of physical activity. Based on previous research, the investigators anticipate the effect size for PA of d = 0.25 (an adjusted for baseline of 5 min moderate-to-vigorous physical activity (MVPA) per day and assuming a standard deviation of MVPA of 17.8 minutes with correlation of 0.59 between baseline and follow-up). The researchers adjusted for clustering at the class level using a correction factor of [1 + (m - 1) x ICC], where m represents the number of participants per class and ICC refers to the intraclass correlation coefficient for PA. Assuming an average class size of 29 participating students, two classes per school and an intraclass correlation coefficient (ICC) for PA of 0.034. Allowing for an expected dropout of 20% at the study endpoint, the required sample size to achieve 85% power with alpha levels set at 0.05 is 70 students by schools.