Risks of Specialized Training and Growth for Injury in Young Athletes: A Prospective Cohort Study
Methods and Study Design: This multi-center prospective cohort study followed injured young athletes recruited from sports medicine clinics and uninjured athletes recruited during their sports physical at primary care clinics. At baseline, all athletes were 8-18 years old and completed a survey reporting training volumes, degree of sports specialization, Tanner stage, and had height and weight measured. This same data was collected from each participant at 6 month intervals for up to 3 years (2010-2012).
Results: There were 1206 participants (50.7% male) who evaluated at baseline while longitudinal follow up data collection is ongoing at time of submission. There were 837 injured participants with a total of 859 unique injuries with 360 uninjured participants that served as controls. Injured athletes were older than uninjured athletes (14.0 +/- 2.2 vs. 12.9 y/o +/-2.6, p<0.001), reported a higher average hours/week playing organized sports (11.3 +/- 6.9 vs. 9.4 +/-8.2 ; p<0.001), and higher average hours/week in total (gym, free play, organized) sports activity (19.7 +/-9.8 vs 17.6 +/-10.3; , p<0.001). Using a six point specialization score designed for this study, injured athletes had a significantly higher degree of specialization than uninjured athletes (3.3 +/- 1.6 vs. 2.7 +/- 1.6; OR 1.27, p<0.001), even after adjusting for hrs/week in total sports activity and age (p<0.001). Injured athletes had similar annual calculated growth rate at baseline (4.75 vs 4.75 cm/yr). Young athletes who participated in more total hours then age (p=0.004) and who participated in > 2 times organized sports then free play (p=0.004) were more likely to be injured. Young athletes at risk for serious overuse injury also participate in more total hours then age and are more specialized.
Conclusions: Injured young athletes are older and spend more total sports hours/week and in hours/week of organized sports. There is an independent risk of injury in athletes that are more specialized, even when accounting for hours/week of sports participation and age. There is also a risk of injury and serious overuse when participating in more sports hours/week then age and all types of injury if participates in more then twice organized sports then free play hours. There does not appear to be a relationship between growth rate and increased risk of injury in the baseline data.
Clinical Relevance: Determining the degree of sports specialization and weekly training volumes may help pediatricians identify young athletes at higher risk for all type and serious overuse injury.
Acknowledgements: 2 Consecutive American Medical Society for Sports Medicine Foundation Grant