PROJECT SUMMARY/ABSTRACT Motorsports drivers have an inherent risk of injury due to racing at high speeds and risk of collisions. Pilot studies have shown stock car drivers and grassroots dirt racing drivers are exposed to low magnitude head acceleration events during green flag racing. At the grassroots level of dirt racing, another pilot study showed that drivers can experience medium to high magnitude head accelerations during crashes within a short time period, unlike stock car crashes. Recent studies have shown exposure to subconcussive head impacts, or head impacts that do not result in clinically diagnosed concussion, can result in microstructural and functional changes to the brain in contact and collision sports. However, there is a paucity of research examining brain injury biomechanics and neurological effects of crashes in motorsport. Additionally, there are numerous disparities in the implementation of safety interventions between the grassroots level and professional levels of motorsport, such as the requirement of head and neck restraints. As a result, there are significantly more injuries and deaths reported for drivers participating in grassroots dirt racing than there are at the highest professional levels of motorsport. By identifying factors influencing kinematic loads and tissue-level brain response of a crash and evaluating acute clinical outcomes of drivers post-crash, future safety interventions could be made to target the disparities seen at the grassroots level. The objective of this study is to use an instrumented mouthpiece sensor to measure head impact exposure in drivers participating in a grassroots dirt racing crashes to identify potential factors that influence kinematic loads and tissue-level brain response and evaluate the neurological effects of crashes. The study team identified in this proposal has extensive history in quantifying head impact exposure, finite element modeling for evaluation of tissue response, and assessing clinical outcomes. A well-developed research and mentoring plan has been prepared fro the successful completion of the following aims. In Aim 1, factors that influence kinematic loads will be identified by outfitting drivers with custom mouthpiece sensors. We will quantify peak head kinematic metrics and compute kinematic-based head injury risk. Relationships between metrics and potential factors will be evaluated. In Aim 2, we will use the mouthpiece sensor data as inputs to an anatomically accurate finite element brain model to assess the tissue-level biomechanical response of the brain to head impact events during crashes. We will quantify various strain and stress-based injury metrics and examine their relationship with the potential factors that were evaluated in Aim 1. Finally, in Aim 3, we will evaluate the effect of crashes on changes in acute clinical outcomes. This study will provide accurate characterization of head motion experienced by drivers during crashes while dirt racing ...