Abstract
Background: Physical inactivity during adolescence contributes to future non-communicable disease risk, yet evidence on contextual barriers in urban Tanzania remains limited. Guided by a socio-ecological perspective, this study assessed physical activity among school-going adolescents in Dar es Salaam and examined social and environmental influences. Methods: A convergent mixed-methods study was conducted in three public secondary schools in Kinondoni Municipal Council, Dar es Salaam, between July and November 2025. Quantitative data were collected from 381 adolescents aged 13–18 years selected through multistage sampling with systematic random selection. Qualitative data were collected through six focus group discussions with adolescents and parents or guardians, and three in-depth interviews with physical education teachers. Weekly physical activity was estimated from self-reported frequency and duration; at least 420 minutes/week was classified as meeting the WHO-recommended level. Quantitative data were analysed using univariable logistic regression, and qualitative data were analysed thematically. Results: Only 15 adolescents (3.9%) met the recommendation. Adolescents aged 16–18 years had lower odds of meeting the recommendation than those aged 13–15 years (OR 0.19, 95% CI 0.04–0.85), whereas boys had higher odds than girls (OR 8.85, 95% CI 1.97–39.78). Parental encouragement was inversely associated with meeting the recommendation (OR 0.28, 95% CI 0.10–0.83), although reverse causality cannot be ruled out. Qualitative findings identified academic pressure, gender norms, social influence, limited facilities, and safety concerns as barriers. Conclusion: Physical inactivity was highly prevalent. Interventions should move beyond awareness raising and address school, social, gender-related, and environmental barriers, particularly among girls and older adolescents.