With youth sport becoming increasingly professionalised and competitive, there has been a trend towards more frequent, structured and high-intensity sport from an early age. Although injuries in adolescents are multi-factorial, sport specialisation and high sport participation volume during adolescence has been linked to increased risk of sustaining injuries, particularly overuse type injuries. Injury risk may be higher during adolescence due to the anatomical changes that occur during the period of peak skeletal growth as well as general decreases in coordination and motor control. Research in this area has grown recently highlighting the need for further evidence to help develop the most appropriate guidelines for adolescent engagement in sport. Therefore, the primary aim of this thesis was to examine the association between specialisation level and injury history, in both the high school sport setting and in the environment of a performance-based sporting academy. A secondary aim of this thesis was to examine the association between specialisation and neuromuscular performance, specifically performance on the Y-balance test. In the first study of the thesis a questionnaire survey was used to gather information from 199 secondary school students aged 12-16-years-old regarding their sporting participation and injury history over the past 12 months. After adjusting for relevant confounding variables (including gender, school year, exceeding a 2:1 ratio of weekly organised sport hours to weekly recreational free-play hours and hours of weekly sport volume), there was no significant association between specialisation level and reporting an injury. However, there was a significant association between reporting a time-loss injury and weekly hours of sport volume (p=0.011). For every hour of additional sport volume, participants were 1.13 (95% CI: 1.03-1.24) times more likely to report a time-loss injury. Furthermore, although there was no statistically significant association between specialisation level and being involved in a high-performance academy, participants from the academy were 6.8 times more likely to exceed the recommended 2:1 ratio of weekly organised sport hours relative to free-play hours (p=0.001). Sport volume was also significantly higher (p=0.006) in the sports academy group (median 8.0 hours) compared to the school group (median 4.5 hours).
In the second study of the thesis, the Y-balance test was used to evaluate balance performance as a measure of neuromuscular control. It has been suggested that sport specialisation may inhibit neuromuscular development due to the reduced range of movement challenges. However, this study did not find an association between specialisation level and Y-balance test performance. Additionally, the second study highlighted that injuries often considered to be growth-related were common in this population of adolescents, with the most common diagnoses being patella-femoral pain and tendinopathy/enthesopathy type injuries to the lower limb, such as Sever’s disease and Osgood-Schlatter’s disease. In conclusion, in this group of NZ adolescents, sport specialisation did not increase the likelihood of reporting a history of injury nor did it result in worse balance performance. However, increased weekly sport volume did increase the likelihood of reporting a time-loss injury. Furthermore, involvement in a performance-based sport academy did not increase single sport specialisation but it did increase sport volumes and decreased recreational free-play. Therefore, monitoring sport volumes may help to decrease injuries in this age group, and this may be even more important in the sports academy setting in New Zealand.