Project Summary The lack of regular physical activity (PA) in over 290,000 individuals with spinal cord injury (SCI) in the United States (US) is an ongoing health crisis. This lack of activity has potentially devastating consequences because low levels of PA in people with SCI elevates the risk of mortality due to cardiovascular diseases, diabetes, and lung disease. Furthermore, low levels of PA in individuals with SCI have been associated with secondary conditions such as pain, fatigue, weight gain, and deconditioning. Regular PA and exercise-based interventions have been linked with improved outcomes and healthier lifestyles among those with SCI. Sensor- based activity monitors can assess PA and exercise interventions by quantifying wheelchair movement, movement of the individual, and physiological changes. However, these monitors do not provide real-time, tailored feedback and recommendations that might help individuals with SCI increase their PA levels in the community. The overarching goal of this proposal is to evaluate a sensor-enabled, just-in-time adaptive intervention (JITAI) strategy to increase and sustain PA levels among individuals with SCI in their communities. The long-term goal of this research is to effectively integrate a mobile health JITAI with existing PA intervention programs to motivate health-related behavior change in individuals with SCI. A primary objective of this proposal is to extend our pilot work to evaluate the integration of a JITAI with a web-based 14-week PA intervention program from the National Center on Health, Physical Activity and Disability (Aim 1). We hypothesize that the integration of web-based PA intervention program with JITAI will result in significantly higher PA levels over 14 weeks compared to the standard we-based PA intervention program alone. A secondary objective of this study is to extend existing algorithms that use commercial wearable technology to robustly detect PA behaviors to facilitate the delivery of tailored just-in-time actionable feedback and PA recommendations for individuals with SCI (Aims 3 and 4). The integration of the JITAI, which provides feedback and PA recommendations due to sensor-based assessments of PA, with the standard web-based PA intervention program will be tested via a clinical trial that combines a randomized controlled trial and a micro-randomized trial. Our team includes investigators with expertise in SCI research, mobile health, PA tracking, and behavioral change interventions. The proposed study will yield novel insights about JITAIs and JITAIs combined with more traditional, web-based PA intervention programs, which will help researchers design engaging PA interventions for individuals with disability in the community that may improve their health and quality of life.