Co-creating and implementing contextually responsive physical activity interventions with low-income adolescents PROJECT SUMMARY Physical inactivity is a public health crisis in the United States (U.S.), with less than a quarter (24%) of children and adolescents and only 3 out of every 4 adults (75%) meeting physical activity guidelines. Historical disinvestments and institutional bias have led to suboptimal access to safe and efficient active transportation options, and to safe, quality places for active play, recreation, and sport in high-need communities, resulting in significant economic and racial/ethnic physical activity disparities. Early adolescence is a critical window of opportunity for establishing lifelong physically active lifestyles and is the stage of life when the steepest declines in physical activity occur. Given that schools can serve as hubs for community and civic engagement, school communities are excellent settings for community-engaged physical activity interventions involving and prioritizing students, parents, and school neighborhood residents at large. To date, however, most school- based physical activity interventions have focused on elementary schools, and on physical education, active recess, and after-school sports programs (i.e., the leisure domain), with less emphasis on active transportation promotion, despite the relatively high independent mobility of middle school students. Further, most environmental strategies to promote physical activity do not include in-depth community-engagement methods, although these approaches can help optimize their contextual responsiveness, effectiveness, and sustainability; and align with the principles of health equity and social justice. We propose a 2-phase, rigorous mixed methods study to identify community-level barriers and facilitators for active transport and leisure physical activity (Phase 1); and to co-create and test the effectiveness and longer-term sustainability of community-based physical activity intervention strategies (Phase 2) in urban, low-income, minoritized middle school catchment areas. Our team includes researchers and community-based partners with expertise in participatory research and extensive knowledge and connections with local communities. Our aims are (1) to identify community-level barriers and facilitators for physical activity in low-income, urban middle school communities with high proportions of minoritized residents, using a comprehensive mixed methods approach (a blended Delphi survey plus Group Concept Mapping method, and quantitative plus qualitative/participatory GIS methods); (2) to equitably engage multi-sectoral and multi-generational community actors for co-creating (co-design, co-implementation and co-evaluation) contextually-responsive intervention strategies to improve equity in access to active transport and leisure in low-income, urban middle school communities with high proportions of minoritized residents; and (3) to conduct ...