Instrumented Mouthguard Acceleration Analyses for Head Impacts in Amateur Rugby Union Players Over a Season of Matches

Background: Direct impacts with the head (linear acceleration or pressure) and inertial loading of the head (rotational acceleration or strain) have been postulated as the 2 major mechanisms of head-related injuries such as concussion. Although data are accumulating for soccer and American football, there are no published data for nonhelmeted collision sports such as rugby union. Purpose: To quantify head impacts via instrumented mouthguard acceleration analyses for rugby union players over a season of matches. Study Design: Descriptive epidemiology study. Methods: Data on impact magnitude and frequency were collected with molded instrumented mouthguards worn by 38 premier amateur senior rugby players participating in the 2013 domestic season of matches. Results: A total of 20,687 impacts >10g (range, 10.0-164.9g) were recorded over the duration of the study. The mean SD number of impacts per player over the duration of the season of matches was 564 +/- 618, resulting in a mean +/- SD of 95 +/- 133 impacts to the head per player, per match over the duration of the season of matches. The impact magnitudes for linear accelerations were skewed to the lower values (S-p = 3.7 +/- 0.02; P < .001), with a mean linear acceleration of 22.2 +/- 16.2g. Rotational accelerations were also skewed to the lower values (S-p = 2.0 +/- 0.02; P < .001), with a mean rotational acceleration of 3902.9 +/- 3948.8 rad/s(2). Conclusion: The acceleration magnitudes and number of head impacts in amateur rugby union players over a season of matches, measured via instrumented mouthguard accelerations, were higher than for most sports previously reported. Mean linear acceleration measured over a season of matches was similar to the mean linear accelerations previously reported for youth, high school, and collegiate American football players but lower than that for female youth soccer players. Mean rotational acceleration measured over a season of matches was similar to mean rotational accelerations for youth, high school, and collegiate American football players but less than those for female youth soccer players, concussed American collegiate players, collegiate American football players, and professional American football players.