Background. Rugby league is a physically demanding team sport and the National Rugby League is the highest-level competition of rugby league in Australia. Frequent tackles and collisions between players result in a high incidence of injury to players. Concussion injuries have been the source of much debate, with reporting varying greatly depending on the definition used. Method. Injury records of 239 players from one professional National Rugby League were analysed during a continuous period of 15 years, with particular interest in the incidence and recurrence of concussions and the change in incidence over time. Result. A total of 191 concussions were recorded, affecting 90 players. The incidence of concussion injuries was found to be 28.33 per 1000 player match hours, with an increase over time ( ). Multiple concussions were recorded for 51 players. Conclusion. A statistically significant increase in the incidence of concussion injuries was found, without a concurrent increase in the number of head injuries or total injuries. New rules which mandate removal of players from the field may be beneficial for protection of players on the long term, although they risk being counterproductive, if they make players less likely to report their symptoms during matches. 1. Introduction The National Rugby League (NRL) is the highest level of professional competition of rugby league in Australia. The playing season runs from March (autumn) to October (spring) each year. Rugby league is a full-body contact, physically demanding team sport consisting of 13 on field players: 6 forwards, 7 backs, and up to 4 interchange players [1–5]. Forwards are chosen for their size, strength, and tackling ability as they are involved in more body contact, whilst backs are often chosen for their speed and agility and are less involved in defensive physical contact [2, 3, 6, 7]. Compared to rugby union, contests for the ball in rugby league are decided in favour of the team in possession for up to 5 tackles with a handover occurring on the 6th tackle to the opposing team [1, 2, 4]. Player tackles and collisions make rugby league a popular spectator sport, but also one with a high reported incidence of injury [8]. Concussion is an injury with relatively low incidence if the injury definition requires players to miss a match, but higher incidence if “non-time-loss” injuries are taken into account [8–12]. 2. Aims A review of the literature regarding injuries occurring in rugby league revealed that previous studies have been of a short duration, and are not concussion injury specific or
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