Concussion is a widespread problem in the military and in sports, with over 1 million estimated sports related concussions occurring in the U.S. each year. However, the mechanism of injury, and therefore diagnosis, is not well understood. Diagnosis of concussion is notoriously difficult because the symptoms, and their interpretation by physicians, are highly variable and subjective. An even greater challenge is that rarely do youth sporting events have trained medical personnel to identify and evaluate injured athletes. Proper management of injury is essential to avoid short-term risks such as re- injury, or even brain hemorrhage, as well as long-term risks ranging from cognitive deficits to dementia. Therefore, an unbiased and quantitative measure of concussion in real-time is needed to prevent further injury. This proposed project centers on the use of a novel instrumented mouthguard that will be worn by collegiate football players in practice and in games to measure three axes of both linear and rotational acceleration. Recent research emphasizes the potential importance of rotational acceleration in concussions as well as the importance of cumulative impacts in long-term neurodegenerative diseases. We hypothesize that this mouthguard can accurately detect magnitudes of linear and rotational acceleration of the head as well as record head impact events that occur during play. The goal of this R21 proposal is to appropriately confirm this hypothesis both in laboratory and on the field. This will enable larger studies to be performed that may better elucidate the mechanism of concussive injury and the risk of neurodegenerative disease. We will do so through the following specific aims: (1) Validate mouthguard kinematics in the laboratory using an instrumented dummy head and (2) Verify impact detection in vivo using practice and game video. In order to validate the mouthguard, head acceleration measurements from mouthguard will be compared to data captured by the instrumented dummy head while undergoing a standard head impact test. In addition, high-speed speed video captured in practice will be used to reconstruct real impacts in 3D to assess validity of laboratory head impact system. Finally, head impact events from mouthguards will be confirmed using game video to modify post-process algorithms in order to optimize the accuracy in detecting real head impact events. Achieving these 2 aims will be the basis for future multi-site clinical studies on the mechanism of traumatic brain injury in multiple sports.