Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Kinesiology

Supervisor

Dickey, James P.

Abstract

Due to the physical nature of the game and repeated head impacts between players each play, the sport of football has one of the highest incidence rates of concussion. With nearly two million participants, this incidence rate translates to a reserved estimate of 100,000 concussions per year due to the contact nature of the sport. Injury thresholds have proven difficult to establish, so American football concussion research has shifted focus to measuring the accumulation of repetitive head impacts. As there are numerous rule differences between Canadian and American football, head impact exposure may present differently for Canadian players. Accordingly, the objective of this thesis was to investigate the effect of cumulative head impacts on Canadian university football players. This was achieved through three research projects using helmet-mounted sensors to monitor head impacts experienced by football players in practices and games, and measuring brain function via saccadic eye movements. Results illustrated that there were no differences in linear and rotational accelerations between striking and struck players during a collision. However, head impacts that occurred during kickoff plays experienced linear head accelerations that were double in magnitude and rotational head accelerations that were triple in magnitude than other special teams, offensive, and defensive plays (Chapter 2). Furthermore, the accumulation of head impacts significantly increased football players’ saccade latencies, which persisted over two successive seasons (Chapter 3). The total number of head impacts experienced during their career was significantly affected by a player’s position, and not their seniority (Chapter 4). In conclusion, this thesis identified football plays that resulted in high magnitude head accelerations, quantified the effect of individual head impacts on brain function using saccade latencies, and characterized career head impact exposure for football players. These results provide evidence that football head impact exposure needs to be reduced for the health of the players. Coaches and league administrators can use evidence-based research to employ strategies to reduce the number of head impacts to the sport of football.

Summary for Lay Audience

American football is one of the most popular sports to watch and play in North America, with over 100 annual million viewers and over two million participants. With its popularity has come the scrutiny regarding concussions and their short-term and long-term effects on player health and safety. Concussions are difficult to diagnose and unique to every individual. While one head impact may concuss a player, the same head impact may not have an effect on another player. Consequently, football research has shifted towards measuring the effects of overall head impact exposure in football athletes. Since there are numerous rule differences between Canadian and American football, head impact exposure may present differently for Canadian players than their American counterparts. Accordingly, this thesis investigated the effect of cumulative head impacts on Canadian university football players. Helmet-mounted, wireless sensors were used to monitor head impacts experienced by football players in practices and games. Rapid eye movements were measured before, during, and after the season to evaluate players’ brain function. Results illustrated that there were no differences in head accelerations between striking and struck football players during a collision. However, head impacts that occurred during kickoff plays were significantly larger than other special teams, offensive, and defensive plays. Furthermore, the accumulation of head impacts significantly increased football players’ eye movement reaction times, which continued over two successive seasons. A player’s position, but not their seniority (freshman, sophomore, junior, senior, fifth year), significantly affected the total number of head impacts experienced during their varsity career. The results of this thesis provide evidence that football head impact exposure needs to be reduced for the health of the players. Coaches and league administrators can use evidence-based research to create strategies to reduce the number of head impacts to the sport of football.

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