ABSTRACT This resubmitted application responds to PA-18-396 Mentored Quantitative Research Development Award (Parent K25). The overall goal of the proposal is to provide support and protected time for supervised research and study to supplement Dr. Robert Dawe?s strong quantitative background as a biomedical engineer, enabling his transition to an independent investigator in NIH-relevant research of age-related mobility impairment. The proposal includes complementary research and career development components. The research component focuses on two understudied aging phenotypes, mobility disability and falls among older adults. Their prevention and treatment is a public health priority that hinges on early identification of mobility limitations. To fill key knowledge gaps toward this goal, a battery of three portable, cutting-edge devices will be used to assess mobility limitations in large numbers of older adults in the community setting, circumventing testing in specialized labs. These novel data have the potential to identify at-risk individuals prior to the onset of disability or a fall, thereby facilitating early, targeted interventions. Furthermore, an Exploratory Aim links this proposal to Dr. Dawe?s past work with brain imaging and also to his long-term goal of elucidating the pathologic basis of age-related mobility impairments. The career development component of the proposal will provide the applicant with additional didactic and clinical training in four targeted areas to facilitate his growth as an independent investigator in his chosen field of aging research: 1) clinical manifestation and treatment of musculoskeletal and neurologic diseases, mobility limitations, and mobility disability in older adults, 2) deploying novel technologies to study mobility and health in community-dwelling older adults, 3) advanced statistical techniques, and 4) neurobiology and neuropathology underlying mobility limitations and mobility disability. Dr. Dawe?s progress will be accelerated by frequent interactions with his Mentor, Dr. Buchman, a pioneer of device-based mobility quantification, and his Co-Mentor, Dr. Bennett, Director of the Rush Alzheimer?s Disease Center. In addition, directed readings, one-on-one meetings, and interactive experiences in lab and clinical settings will be provided by an Advisory Committee composed of knowledge leaders in each of the four aforementioned training areas (Drs. Block, Hausdorff, Wimmer, Yu, Schneider). Additional interactions are planned with physicians in specialty clinics at Rush (Drs. Arvanitakis, Goldman, Song), pathologists specializing in motor-related anatomy outside of the brain (Drs. VanderHorst, Pytel) and investigators working with a variety of behavior quantification technologies (Drs. Lim, Kaye, Levine). Regular participation in conferences, seminars, and courses in several key areas rounds out the training plan. Dr. Dawe?s success in completing the research and career development components will be validated by his submission of an R01 proposal by the end of the K25 funded period.