ABSTRACT Sepsis, an exaggerated response to infection, affects all ages, but it is more prevalent in older adults. Older sepsis survivors are commonly discharged to long-term acute care facilities, where they often die within 1 year. We believe that those who return home from the hospital lose the momentum of physical function improvement after early in-hospital rehabilitation and often face exacerbation of comorbidities and decline in physical function. Based on our longitudinal observational data, older sepsis survivors have poor health status and physical function lasting at least 1 year after sepsis, and in contrast with younger survivors, older patients do not regain their function. Our aging research suggests that physical activity interventions prevent mobility disability in rather healthy older adults, but older sepsis survivors will be profoundly frailer, more sedentary, lower- functioning and will unlikely be capable of traveling to participate in supervised exercise training programs in our research facilities. Currently, we are unaware of any home-based therapeutic approaches to improve physical function of older sepsis survivors. Current mobile health applications can deliver structured home-based exercise programs to reach daily activity goals. For example, the Blue Marble Health Platform (BMHP), developed and validated with the support of NIH contains over 100 avatar-guided strengthening, balance, and aerobic exercises, along with 23 standardized assessments and a personal health diary. This digital and remotely monitored exercise training program might be promising for sepsis survivors with poor health status, who are unlikely to be able to travel to participate in exercise interventions. Our proposed study will test the safety, feasibility and efficacy of a novel 12-week physical activity intervention to improve physical function in older sepsis survivors utilizing an app-based digital exercise training platform. We propose to randomize 40 sepsis survivors (aged >65 years) with an SPPB score <6 at the time of their discharge to home from the hospital into the intervention or a standard care control group. Both groups will receive a tablet with the BMHP app, which contains all of the physical function assessments, and a health diary. The intervention group will also receive personalized avatar-guided exercises as well as text message reminders to exercise for 30min each day, 5 days/week. For the control group, participants will record their daily activities using the BMHP health diary. A research coordinator will call all participants weekly to ask questions about their health status and remind them to charge the tablets. At baseline and 12-week follow-up, participants will use the app to complete the app- guided physical function assessments and we will measure activity levels using hip-worn accelerometers. This project will be the first to test the safety, feasibility and efficacy of a digital physical activity intervention in t...