A Mixed Effect Analysis of Head Impact Accelerations During Rugby Head Impacts Under Different Gameplay Conditions.

PURPOSE: Exposure to head acceleration events in rugby can lead to both physical and mental health problems, even without a diagnosed traumatic brain injury. This study aimed to explore relationships between gameplay head impact conditions and head acceleration metrics experienced by rugby players. METHODS: Using head impact kinematic data from two high school rugby union teams in New Zealand (one male and one female), linear mixed-effect models identified significant trends between gameplay techniques, head impact mechanisms, and the resulting linear and rotational peak accelerations and injury criteria. RESULTS: Head impacts to bony body regions, crushing head impacts, and head impacts to the ground produced the highest linear and rotational acceleration metrics. Impacts between the head and the ball also resulted in higher rotational accelerations than head impacts with the hip and soft body regions. Indirect head acceleration events and head-to-tackle pad impacts resulted in the lowest acceleration metrics. Males showed lower acceleration metrics during training drills, mauls, and scrums than females. Impacts to the chin resulted in the highest peak accelerations, followed by impacts to the rear of the head, with impacts to the front, top, or side of the head resulting in the lowest acceleration metrics. Indirect head acceleration events resulting in flexion/extension or lateral rotational motion induced the highest acceleration metrics. The tackling technique had limited effect on the acceleration metrics of the tackler, with tackles made to the torso/hip region and upper leg region, both with the head beside the tackle location, resulting in the highest peak accelerations. CONCLUSION: This analysis could indicate gameplay events that require further investigation to improve player safety without employing protective equipment.