Effects of a School-Based Physical Activity Intervention on 24-Hour Movement Behaviours and Motor Development in Preschool Children - Study Protocol

This protocol describes a quasi-experimental controlled study evaluating the effects of the Super Quinas in Preschool programme on 24-hour movement behaviours and motor development in preschool children aged 3-6 years. The intervention consists of one additional structured 60-minute physical activity session per week for 12 weeks, delivered by a qualified exercise professional in a public preschool in Maia, Portugal. Four classes (\~80 children) are allocated at the class level: two to the intervention condition and two to the control condition (usual curricular Physical Education). Baseline data collection (T0) was conducted between 4 and 18 March 2026; the intervention commenced on 25 March 2026. Subsequent assessments are planned for early May (T1, mid-intervention), end of June (T2, post-intervention), and mid-September 2026 (T3, follow-up). Primary outcomes are 24-hour movement behaviours (ActiGraph GT3X accelerometry) and motor competence and physical fitness (Motor Competence Assessment + PREFIT subtests). Secondary outcomes include executive function (HTKS; Day-Night Stroop) and socioemotional regulation (SDQ). Statistical analyses will use longitudinal linear mixed-effects models under an intention-to-treat framework.