Traumatic Brain Injury (TBI) is the damage caused to the brain by an external force causing rapid acceleration and deceleration of the brain, and a sub-concussive impact is defined as a bump, blow or jolt to the head not resulting in any apparent symptoms. Within the United States, around 1.7 million people suffer from TBI, of which sports-related injuries are the cause for one-third of the head injuries. It is estimated that approximately 20% of professional boxers experience at least one incidence of concussion or knockout in their careers and 40% of retired boxers suffer from lasting effects ranging from headaches, nausea and dizziness to Parkinson’s Disease, and dementia. Despite visible recovery from the initial injury, many individuals experience secondary neurodegeneration that can lead to gradual tissue deterioration and severe neurodegenerative diseases. The purpose of this research is to investigate the acute effects of repetitive sub-concussive impacts that are commonly seen in sports to study the progression neuropathology that would help advance the research and understanding of brain health among athletes worldwide.

Since there are no existing models that adequately replicate the delivery of repetitive subconcussive head impacts that is representative of head injuries in a sport, the first goal in this research was to develop a rodent model that delivered sub-concussive impacts and study its effects on behavior and on the resulting neuropathology in the brain. Following observations in an animal model, evoked response potential (ERP) of boxing participants were measured and compared after one year to study the effects of multiple sub-concussive impacts. Of the different types of wearable instrumentation that wirelessly measure head impact acceleration parameters, instrumented mouthguards (iMG) are preferred due to their tight coupling to the skull. Hence, this research investigated the accuracy of two different iMGs when subject to simulated punches as seen in boxing, on the jaws of post-mortem human subjects.

The results from these studies provided important insights that help understand the acute effects of repetitive sub-concussive impacts in a rodent model. The lack of any difference in behavior accompanied by damage to the axonal structure in rats is similar to boxers returning to their daily routine after a match where no visual symptoms are seen, but this may underline a progression of deteriorating neuropathological cascade. Further experimental studies are needed to confirm the progression of this pathology, but it is wellknown that retired boxers are susceptible to neurodegenerative effects. The lower ERP data in professional boxers who have more than 10 years of experience in the sport compared to amateur boxers with less than 5 years of experience also indicated a potential decline in cognition. Lastly, this study reported a contrast in performance of the iMGs in cadavers subject to jaw impacts compared to the close to perfect accuracy observed in idealistic tests in anthropometric test dummies (ATDs). This highlights that these iMGs may not be well suited to accurately measure impacts on the jaw.

The findings from this research underscore the importance of understanding the acute effects of repetitive sub-concussive impacts and their potential long-term implications. The development of effective models and accurate measurement tools is crucial for advancing research in brain health among athletes and for developing preventive and therapeutic strategies.