PROJECT SUMMARY/ABSTRACT Physical activity is a protective factor of Alzheimer's disease and related dementias. While there are many benefits to physical activity, adults with intellectual disability (ID) often do not engage in healthy physical activity levels. With higher rates of early-onset dementias and age-related conditions in adults with ID, developing improved strategies and programs that promote physical activity in this population is critical. Barriers to physical activity include a lack of inclusive physical activity opportunities, access to community exercise facilities, and reliance on external supports. The purpose of this NIH Stage 1 mixed methods study is to test the feasibility, acceptability, fidelity, and prepare for a Stage 2 efficacy study of a multi-level physical activity intervention. Step It Up+ is a 16-week multi-level program that utilizes self-management strategies, including goal setting, self-monitoring, and visual supports to help adults with ID engage in the program more independently through an interactive web-based dashboard. Adults with ID work with a support coach to increase daily step counts and time spent in moderate-to-vigorous physical activity by engaging in individualized aerobic and strength training activities. Aim 1 is to modify, adapt, and refine our existing Step It Up home-based program at the individual level of the socioecological model to include the community level through a weekly inclusive group fitness class (Stage 1A). This phase will include usability testing, pilot testing of the RCT assessment battery, and semi-structured interviews with adults with ID and surveys and focus groups with additional stakeholders (parents, caregivers, and exercise professionals) to demonstrate the features and functionality of the interactive web-based dashboard. Aim 2 is to conduct a pilot randomized controlled trial (Stage 1B). This phase will use a waitlist control experimental design with 120 adults with ID in two sites (North Carolina and Texas). Feasibility will be assessed quantitatively by measuring recruitment, attendance, and completion rates. Qualitative data from focus groups and interviews will augment the feasibility quantitative findings and provide feedback on consumer acceptability. Content experts will evaluate treatment fidelity by reviewing a subsample of video-taped sessions. We will measure the impact of Step It Up+ on increasing physical activity and explore hypotheses regarding the potential efficacy of the intervention's effect on physical activity. We will compare primary outcomes of physical activity using daily step counts, activity intensity minutes, body composition, and secondary outcomes of wellbeing, functioning, and social belonging. The findings from this project will lay the essential groundwork for a large-scale, for an R01 to conduct a Stage 2 primary prevention trial in adults with ID who are pre-symptomatic of AD/ADRD. Our long- term goal is to promote healthy physical...