The OBAFIT project aims to examine the patterns of physical activity, sedentary activity and health-related physical fitness of the boys and girls enrolled in schools of Primary Education and Secondary Education in Castilla-La Mancha (Spain). The design of the project is observational/cross-sectional. Through an epidemiological orientation, it proposes a representative sampling of a multistage type of the Castilian-La Mancha population aged 6 to 16 years. The subjects that will make up the sample will be selected from among the 724 Castilian-La Mancha schools with teachings in the Primary Education stage, and among 373 Secondary Education schools. To ensure the heterogeneity of the population, both public and private centers will be selected, and proportionally between centers that have Healthy School Programs (PES) from those that do not. The sample will be multistage, randomized and stratified according to province (Albacete, Ciudad Real, Cuenca, Guadalajara and Toledo), area (urban, semi-urban, rural), sex (men, women) and age (one group for each age group).

The OBAFIT project was designed to provide a public tool where PA habits, sedentary behaviors and the health-related physical fitness of school children from Castilla-La Mancha (a Spanish region) could be visualized. OBAFIT also allows physical education teachers at participating schools to monitor and observe the evolution of these variables in their students.

For this, the schooling data provided by the Consejería de Educación, Cultura y Deportes de la Junta de Comunidades de Castilla-La Mancha (Ministry of Education, Culture and Sports of the Community Board of Castilla-La Mancha) are considered: the population enrolled in the region from the first to the sixth year of Primary Education amounts to 131,903 students (63,488 girls; 68,415 boys) distributed in the five provinces (Albacete 24,143; Ciudad Real 31,053; Cuenca 11,001; Guadalajara 17,560; Toledo 48,146) both in public (106,366) and private (25,537) schools.

In the case of Secondary Education and the first year of high school, the number of students stands at 98,745 (50,807 men and 49,267 women) from the five provinces of the region (Albacete 19,016; Ciudad Real 23,599; Cuenca 8,971; Guadalajara 12,827; Toledo 34,332) of public centers (80,996) and private (19,078).

The sample size, calculated through the Edidat 4.2 software, is 631 subjects for the Primary sample and 631 for the Secondary sample (assuming normal distribution). A confidence level of 95% and a margin of error of 3% have been considered, and the CVR associated with low CRC with a prevalence of 18% is assumed as the parameter of greater variance. If the same level of confidence and margin of error for both sexes are considered, the sample would amount to 1,262 for each educational level. Assuming a non-response rate of 30%, the final sample size is estimated at 1640 students in Primary Education and 1640 for Secondary Education.

The participants that will make up the sample will be selected from the 724 Castilian-La Mancha schools with education in the Primary Education stage, and from 373 Secondary Education centers. Both public and private centers will be selected. The sample will be multistage, randomized and stratified according to province (Albacete, Ciudad Real, Cuenca, Guadalajara and Toledo), area (urban, semi-urban, rural), gender (men, women) and age (one group for each section of age).

Once the sample size has been determined, a lottery of schools classified based on the aforementioned criteria is carried out, considering in all cases the proportionality in the number of students. For this, a multistage method with proportional probability will be used using SPSS 24.0 software. Approximately 48 centers for Primary Education and 55 for Secondary Education will be selected, taking into account that there are 6 Primary courses and 4 in E.S.O. (Spanish system) in addition to 1st year of high school In the selected schools, three boys and three girls will be randomly chosen per group-class and level, on which the different instruments will be applied. A priori, due to pedagogical and operational issues in the administration, proportional age preselection will not be carried out (for the same group-class). Since all students in the same class-group will have the same probability of being selected, the age and sex quotas will be corrected at the end of data collection by a weighting system.

Inclusion Criteria:

- Be enrolled in any school in Castilla-La Mancha (primary or secondary, public or private, rural or urban).

Exclusion Criteria:

• Temporary injury or disability that prevents physical testing.
• Clinical diagnosis of diabetes or diseases not related to nutrition.

Boys and girls aged 6 to 16 years enrolled in Primary and Secondary Education schools in Castilla La Mancha.