PROJECT ABSTRACT Promoting health-enhancing and sustainable physical activity levels across childhood and adolescence contributes to adult health. Health disparities are present in ethnic minority children and are linked to physical inactivity. The Children’s Health Activity Motor Program (CHAMP) is an evidence-based intervention that demonstrates impactful results on motor performance, perceived motor competence, and physical activity in physical education and movement-based settings. Currently, 10 million children participate in afterschool programs (ASPs) each day, and ASPs provide a great opportunity to enhance children’s health outside of the regular school environment, particularly given the decline in physical education. This proposed randomized cluster, controlled trial will examine the immediate (pre- to post-test) and sustained (1-year post-intervention follow-up) effects of CHAMP-ASP on physical activity (primary outcome), motor performance, perceived motor competence, health-related physical fitness, and weight status. CHAMP-ASP will be implemented by ASP staff and will be conducted in ASPs located in Lansing and Ypsilanti, Michigan. The ASPs will include a high minority population. Children (N = 264; CHAMP-ASP=132 and control=132) K-2 graders (typically ages 5-8 years) will participate 35 minutes/day X 3 days/week for 19 weeks (dose of 1995 minutes). The aims are to: a) examine the immediate and sustained effects of CHAMP-ASP on physical activity, motor performance, and perceived motor competence relative to the control ASP, b) examine the immediate and sustained effects of CHAMP- ASP on secondary health outcomes - health-related physical fitness (cardiorespiratory fitness, muscular strength), and weight status compared to children in schools randomized to control ASP, and c) determine if perceived motor competence mediates the effect of CHAMP-ASP on moderate-to-vigorous physical activity. The long-term goal is to provide a sustainable, ecologically-relevant, and evidence-based program during the early elementary years that is health-enhancing and increases physical activity in the ethnic minority population. Findings could significantly influence future physical activity interventions and support a sustainable, ecologically-relevant (delivered by ASP staff) evidence-based program (i.e., CHAMP) that contributes to long-term health-enhancing physical activity and health in children.