Introduction: Recent trials with adolescents have intervened to increase physical activity levels. Primary results report on the outcome (change in physical activity) with less focus on the evaluation of the intervention strategies and activities. This dissertation project presents an in-depth analysis of the extent to which Trial of Activity of Adolescent Girls (TAAG), a physical activity intervention targeting middle school girls, was implemented and received in three Maryland schools. Individual, social, and environmental factors were explored.

Methods: Responses from select quantitative process evaluation data were used to assess dose, fidelity, and reach for each TAAG component. Information was integrated with data from nine focus groups with girls and 24 in-depth interviews with school staff, community partners, and TAAG university staff, who were key participants of the intervention activities. The focus group and interview data were analyzed using thematic methodology to identify key concepts, categories, and themes.

Results: Implementation of the intervention varied by school and by intervention component. Qualitative interviews suggested that school differences could be attributed to school staff buy-in, administrative and faculty/staff support, and student behavior. Study staff implemented the intervention to teachers with higher levels of dose, fidelity, and reach than what teachers delivered to students. Notably, fidelity for physical education (PE) concepts and health education with activity challenges (HEAC) lessons was lower. Class observations indicated that PE objectives were observed 6% to 93% of the time, and 38% to 82% of HEAC lesson components were fully completed. Reasons reported by teachers for low fidelity were lack of time, administrative barriers, and limited space for activities. Reach for most components were high. Participation in after school programs ranged from approximately 9-22 girls. Girls reported lack of transportation, cost of programs, lack of interest, and time conflict as reasons for not joining programs.

Conclusion: To maximize intervention efforts, it is important for researchers to decrease factors that negatively influence how well physical activity initiatives are executed as planned. Different data sources can provide information to better understand factors influencing program implementation.