Introduction: Sports-related concussions are a major health concern in contact sports. There is a high incidence of concussions in adolescent rugby union when compared with other sports. Primary prevention of sport-related concussions is a key priority for sport governing bodies and health practitioners. Concussion prevention strategies have been successfully implemented in many sports. While rule changes, use of protective equipment and neuromuscular training programs have been effective in reducing concussion injuries, concussion rates remain high. There is growing interest in the role of neck muscle strength in mitigating the risks of concussion in contact sports, yet there is currently limited evidence to support this. The aim of this study was to determine if neck strength was associated with an increased risk of in-season concussion injuries and to establish clinical cut-off values for high school rugby union and league athletes.

Methods: A prospective observational study including adolescent males aged 15 to 18 years was conducted. Participants were recruited from one school in Queensland, Australia. Players in the Firsts and Seconds rugby union and league preseason training squads were included. Isometric neck strength was measured using a pull dynamometer, with participants seated, and a harness strapped around the head. Maximal isometric neck strength was assessed for flexion, extension, and lateral flexion. Three repetitions of three second contractions were recorded. The maximal contraction was recorded in kilograms (kg) and normalised to body weight as Newtons/kilogram (N/kg). In-season concussion injuries were recorded by school medical staff. Preliminary multivariate analysis-of-covariance models were conducted to investigate differences in neck strength in players who sustained a concussion during the season. If significant, receiver operated characteristics (ROC) curves were used to determine optimal cut point for each variable. Unadjusted odds ratios were estimated from cross tabulation chi-squared test. Significance was set at p < 0.1.

Results: A total of 43 players were assessed during preseason. Eleven players sustained a concussion during the school rugby union and league season. Players who sustained a concussion during the season had weaker neck extension strength in kilograms (p = 0.049) and when normalised to body weight (p = 0.047). The clinical cut point for extension strength was 32.1 kg (Sensitivity 0.69, Specificity 0.58) and 4.13 N/kg (Sensitivity 0.47, Specificity 0.92). The unadjusted odds ratio indicated that if a player had weaker neck extension strength (< 4.13 N/kg, p = 0.06) the odds of a concussion were 4.4 times higher (CI 0.8-23.4, p = 0.09). There were no differences for other directions of neck strength.

Discussion: Results indicated that players with weaker neck extension strength had increased odds of sustaining a concussion during the playing season. Considering that the most common mechanism of injury for concussion is tackling and being tackled, it is not surprising neck muscles are an important consideration as they can dissipate forces during impact. The results provide supporting evidence that interventions targeting neck strength could reduce the risk of concussion.

Impact/Application to the field: •Neck strength is an important consideration for concussion injuries in adolescent athletes. •Increasing neck extension strength may reduce the risk of concussion.

Declaration: My co-authors and I acknowledge that we have no conflict of interest of relevance to the submission of this abstract.