Biomechanics of head impacts in men's university ice hockey

Ice hockey has one of the highest incidences of impacts to the head among team sports. Most head impacts do not result in diagnosed brain injury. Yet growing evidence shows that repetitive head impacts, even at sub-concussive levels, have serious long-term, negative effects on brain health. Efforts are required to reduce the number and severity of head impacts during game play. The goal of this thesis is to generate new evidence on how head impacts occur in ice hockey, and thereby provide an improved basis for preventing and mitigating the severity and number of these events. In partnership with the SFU Men's Ice Hockey team, we collected and analyzed video footage (N=836), paired with head kinematic data from helmet-mounted sensors (N=234) of head impact events. From video analysis, we found that head impacts occurred most often to players checked along the boards in their offensive zone, who did not have puck possession. Glass-to-head impacts represented 28% of cases, four times as common as board-to-head impacts. Hand-to-head impacts accounted for 22% of cases, twice as common as shoulder- or elbow-to-head impacts. By combining video and sensor data, we found that head rotational velocities were greater for impacts where the player was visibly affected by the collision and for impacts which received a major penalty. Building on our evidence that shoulder checks represented the most common and severe body part to impact the head in men's university hockey, we acquired laboratory measures of shoulder displacement and force production as players delivered shoulder checks at varying intensities (impact velocities). Analyzing our results with a mass-spring-damper model, we found that the effective stiffness and damping coefficient of the shoulder averaged 12.8 kN/m and 377 N-s/m, and the effective mass averaged 40.0 kg, or 47% of total body mass. By providing objective evidence on how head impacts occur in hockey, and quantifying the dynamics of a common and severe scenario (shoulder-to-head collision), our results should inform improvements in prevention through changes in rules of play, equipment/rink design, player training, and injury screening.