Background, rationale, and methodological overview of the REACT project-return-to-action on growth, motor development, and health after the COVID-19 pandemic in primary school children.

OBJECTIVES: The REACT project was designed around two main aims: (1) to assess children's growth and motor development after the COVID-19 pandemic and (2) to follow their fundamental movement skills' developmental trajectories over 18 months using a novel technological device (Meu Educativo®) in their physical education classes. In this introductory article, the first of the Journal's special issue dedicated to REACT, our goal was to present the project rationale, its methodology, training and certification of the team, statistical approach, quality control, governance, and study management. METHODS: We sampled 1000 children (6-10 years of age) from 25 of the 32 primary schools in Matosinhos, northern Portugal. The protocol included a set of variables clustered around the child (growth, physical fitness, fundamental movement skills, and health behaviors), family (demographics, socioeconomic status, parental support for sports participation and physical activity), school (policies and practices for health behaviors, infrastructure for physical education and sports practices), and neighborhood and home environments (safety, sidewalks, sports facilities, as well as children electronic devices and play equipment at home). A set of standard protocols were implemented in REACT together with a rigorous system of training and certification of all members of the research team. This was complemented with a pilot study to assess, in loco, the quality of data acquisition, data entry, and control. DISCUSSION: Results from REACT will provide school administrators and teachers with novel and far-reaching information related to children's growth and motor development as well as health behaviors after the COVID-19 pandemic. It will also provide city-hall education officials with insight regarding children's physical fitness, fundamental movement skills, and sports practices that will be of great importance in devising novel intervention programs to increase health-enhancing physical activity, and combat sedentariness and obesity. Finally, it will offer parents a wealth of information regarding their children's growth, motor development, and health.