Context: Although considerable cross-sectional evidence exists regarding the association between sport specialization and injury, sport-specific prospective research is lacking. Similarly, sport specialization is associated with impairments in sleep and subjective well-being in youth athletes, but it is unknown whether this increases the risk of illness. Objective: To determine the relationship between sport specialization status and in-season injury and illness risk in elite female adolescent soccer players. Design: Prospective Cohort Study Setting: Preseason evaluation of maximal aerobic capacity (VO2max) and sport specialization, and in-season self-reporting of daily training load (session-rating of perceived exertion), injury and illness resulting in lost sport participation time. Participants: 80 female youth soccer players (ages 13-18) from a local youth soccer organization. Main outcome measures: Sport specialization status, injury and illness incidence during two 4-month competitive soccer seasons. Athletes were considered specialized if they participated in soccer exclusively versus multiple sports during the year. Mixed effects logistic regression models were used to individual injury and illness (yes/no) during the study period, using sport specialization, age, and training load as fixed effects and individual athlete as a random effect. Results: Specialized (n=46) athletes did not differ from non-specialized (n=34) athletes with respect to age, preseason physical activity, VO2max or in-season training load (all p>0.05). No difference was seen in the proportion of individuals from each group that reported an in-season injury (specialized = 19% v 17%, p=0.83) or illness (40% v 38%, p=0.82). After adjusting for age and training load, individual injuries (OR= 0.86 [0.26,2.8], p=0.81) and illnesses were not significantly predicted by specialization (OR= 1.06 [0.45,2.5], p=0.89). Conclusions: After adjusting for age and training load, sport specialization status was not associated with in-season injury or illness risk in elite female soccer players.

Dr. Watson serves as the Chief Medical Adviser for the Elite Clubs National League

This study was partially funded by the Young Investigator Award from the American Medical Society for Sports Medicine

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Approval for the study was provided by the Health Sciences Institutional Review Board at the University of Wisconsin (2014-0373)

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