Head Acceleration Events Measured by Instrumented Mouthguards in Elite Australian Football

BACKGROUND: The consequences of exposure to head acceleration events (HAEs) in collision sports, including Australian Rules football, are a growing concern. Instrumented mouthguards (iMGs) now enable accurate quantification of HAEs in sport; however, little is known about HAE incidence and mechanisms in Australian Rules football. We aimed to measure HAEs in elite Australian Rules football players, and evaluate the influence of playing position and match event on the incidence and magnitude of HAEs in men and women. iMG data were collected from Australian Football League (AFL) and AFL Women's (AFLW) players in 2023 utilising the HIT-IQ Nexus Gen III iMG, targeting 500 player-matches per sex. Match footage was synchronised with iMG data for video verification and match play coding. RESULTS: Three hundred and eleven players contributed iMG data in the analyses, including 126 men (median matches per player: 3 (interquartile range [IQR: 2-6]) and 185 women (median: 3 [IQR: 1-4]). Men had a higher mean incidence of HAEs ≥ 8 g per match than women (5.7 [95% confidence interval CI: 5.0-6.4] vs. 3.0 [95% CI: 2.8-3.3]), however the incidence was comparable when adjusted for time (3.6/hour [95% CI: 3.2-4.1] vs. 3.1/hour [95% CI: 2.9-3.4]). Men recorded higher maximum single-impact peak linear acceleration (PLA; median 31 g vs. women: median 22 g; p < 0.001) and peak rotational acceleration (PRA; median 3.0 krad/s² vs. women: 2.4 krad/s²; p < 0.001) per match. Conversely, women experienced greater PRA per impact (median 1.4 krad/s² vs. men: 1.2 krad/s²; p < 0.001), while PLA was similar (men: median 14 g, women: median 13 g; p = 0.330). The leading match events resulting in HAEs were marking contests (1.0/hour) in men and contested ball situations (0.8/hour) in women. HAE incidence and magnitude were generally comparable across playing positions, except for men's rucks, who experienced significantly higher incidence of HAEs (6.5/hour) than forwards (3.6/hour), midfielders (3.2/hour), and defenders (2.7/hour). CONCLUSIONS: This study highlights differences in HAE incidence, magnitude, and mechanisms by sex, playing position, and match events in elite-level Australian Rules football. These findings provide insight into impact exposure patterns and may inform targeted skill development and policy adjustments to enhance player safety.