Physical activity promotion among youth is critical for cardiovascular disease prevention. Despite available evidence-based approaches for physical activity, implementation remains a challenge, especially in schools. Therefore, there is an urgent need to develop effective implementation strategies to improve the dissemination and implementation of evidence based physical activity approaches for children. The purpose of this four year K01 award is to prepare Dr. Timothy J. Walker with the training and experience necessary to achieve his career goals of becoming an independent investigator and leader in the field of implementation science and physical activity promotion. This proposal includes three training objectives: 1) gain proficiency in implementation research; 2) build analytic skills to use multilevel models and Bayesian statistical approaches in implementation research; and 3) increase competency in conducting school-based physical activity research. Dr. Walker has assembled a mentorship team of experts in implementation science (Dr. Maria Fernandez, primary mentor), applied statistical methods (Dr. Charles Green, co-mentor), and physical activity research (Drs. Harold Kohl and John Bartholomew, co-mentors). The proposed study sets out to improve the implementation of active learning, which is a school-based evidence-based approach that incorporates physical movement into academic lessons. The study rationale is that active learning approaches are effective for increasing children's physical activity, yet there are large gaps in research about their implementation in practice. The study aims are: 1) develop an implementation strategy to improve the use and sustainment of active learning approaches in elementary schools and 2) conduct a feasibility study to evaluate the impact of the developed implementation strategy on the implementation and effectiveness of active learning. Aim 1 will use Intervention Mapping, a systematic approach to develop a scientifically-based multifaceted implementation strategy. Aim 2 will use a quasi-experimental design to examine acceptability of the implementation strategy and its impact on implementation fidelity. Aim 2 will also examine the preliminary effectiveness of active learning. This study is highly significant because it addresses physical inactivity among children in schools where there is an urgent need for implementation support. If effective, the developed implementation strategy has the potential to improve the use of active learning and reach millions of students across the US. The study is innovative because it targets a novel approach for active learning where there is limited research about implementation strategies to support the use of such approaches. It also uses a novel framework to guide implementation strategy development, and Bayesian statistical methods to determine whether the implementation strategy warrants further testing. Results from this study will enhance the ability to scale-...