Project Summary Each year, as many as 250,000 individuals tear their anterior cruciate ligament (ACL) in the United States, with over 75% undergoing an ACL reconstruction (ACLR). Despite completion of formal rehabilitation, a significant portion of young individuals demonstrate persistent functional deficits at the time of return to pre- injury sports participation and up to 30% of young, active individuals sustain a second ACL injury within months of returning to sports participation. Traditional biomechanical methodologies assess individual components of the movement system. However, the application of nonlinear methodology may uncover the underlying mechanisms between the components of movement faults in a way that has the potential to uncover new information about how the entire movement system interacts with its environment. There are many implications for nonlinear methodology in rehabilitation research. As physical therapists, we are movement experts and tailor our treatments to improve and enhance our patients’ abilities to move effectively. It is possible that the ability to responsively tailor movement to the demands of the context in which they are imbedded may prevent injury, whether that be an athlete sustaining a second ACL injury or an elderly individual sustaining a fracture due to a fall. The innovative research described in this proposal has the potential to advance current knowledge in ACL research and inform clinical care for athletes returning to sports after an ACL injury as well as in other clinical populations. My goals for the training period include refining skills in rigorous research study design, applications of nonlinear methodology and systems science theory, leadership and research dissemination and professional development. The proposed research will take place at Ohio State University at the Martha Morehouse Pavillion and the Jameson Crane Sports Medicine Institute. Both the Sports and Tactical Athlete Injury Resiliency Science Laboratory in the Martha Morehouse Pavillion and the Jameson Crane Sports Medicine Institute have dedicated faculty and staff members to ensure accurate and streamlined data acquisition with dedicated time for student research with a multidisciplinary environment housing surgical suites, physician/surgeon’s offices, a physical therapy clinic, surgical skills laboratory, and dedicated research office space with data analysis software to provide a productive environment for analysis, interpretation and manuscript development. The environment affords many collaborative interactions and ample resources to complete all data collections outlined in this fellowship application. My sponsorship team consists of four university faculty members (3 at Ohio State University and one at the University of Cincinnati). My sponsors have diverse areas of expertise that are directly in line with their defined areas of contribution to the research and specific roles and responsibilities over the course of th...