Background Concussion is common in the sporting arena and is often challenging to diagnose. The development of wearable head impact measurement systems has enabled measurement of head kinematics in contact sports. Objectives The objective of this systematic review was to determine the characteristics of head kinematics measured by an accelerometer system among male athletes diagnosed with concussion. Methods A systematic search was conducted in July 2015. Inclusion criteria were English-language studies published after 1990 with a study population of male athletes, in any sport, where objectively measured biomechanical forces were reported in the setting of a concussive event. The random effects meta-analysis model was used to combine estimates of biomechanical force measurements in concussed athletes. Results Thirteen studies met the inclusion criteria, the majority of which were conducted with high school and college football teams in the US. Included studies measured a combination of linear and rotational acceleration. The meta-analysed mean peak linear head acceleration associated with a concussive episode was 98.68 g (95 % CI 82.36-115.00) and mean peak rotational head acceleration was 5776.60 rads/s 2 (95 % CI 4583.53-6969.67). The estimates of the biomechanical forces were consistent across studies, with I 2 values of 0 % for both metaanalyses. Conclusions Head impact monitoring through accelerometery has been shown to be useful with regard to characterising the kinematic load to the head associated with concussion. Future research with improved clinical outcome measures and head kinematic data may improve accuracy when evaluating concussion, and may assist with both interpretation of biomechanical data and the development and utilisation of implementation strategies for the technology.
Objective: To determine the rate of injury in junior Australian football, and to describe the patterns and severity of these injuries across nine levels of play (U9 to U18). Design: Prospective cohort study. Setting: Junior Australian football games and training sessions were observed for 54 teams from New South Wales and Victoria over the 2004 playing season. Participants: Six teams from each level of play were invited to participate in the study. Overall, data were collected for 51 teams over 40 208 hours of player exposure. Independent variables: Participation and injury data were collected prospectively. Main outcome measures: Injury was defined as "any trauma that causes some disability or pain''. Injury severity was identified by the action of players immediately after the injury event. Results: The overall injury rate was 18.0 (95% CI 16.6 to 19.3) injuries per 1000 player hours. The main cause of injury was body contact (67.3%). There was an increased frequency of sprains and strains, and injury severity with increasing level of play. The rates of injury for players who stayed off the field (6.4 injuries per 1000 hours, 95% CI 5.6 to 7.2) or were advised to seek off-field medical advice (5.0 injuries per 1000 hours, 95% CI 4.3 to 5.7) were low. Conclusion: Compared with the adult game, junior Australian football is relatively safe. However, injury rates increase as children progress across age-determined levels of play towards the more adult form of the game.