Associations of Sport Participation and Training Volume With Overuse Injuries in Japanese Male Youth Soccer Players: Implications for Early Sport Specialization

Background: Sport specialization is associated with increased risk of overuse injuries. However, the effects of sport specialization on the risk of overuse injury may differ by specific sport and sociocultural parameters. This study aimed to determine the associations of sport participation and training volume with previous overuse injuries in Japanese male youth soccer players. Hypothesis: Being highly specialized before the age of 12 years and high training volume relative to participant age would be associated with a history of serious overuse injury. Study Design: Cross-sectional study. Level of Evidence: Level 3. Methods: Survey data were collected from male youth soccer players (seventh-ninth grade) during midseason of the 2020-2021 academic year. Participants completed a questionnaire regarding their status of sport participation (single- and multisport athletes), weekly sports volume in first- sixth grade and injury history in the previous year. Odds ratio (OR) was calculated to identify associations of specialization and training volume with a history of serious overuse injury. Results: A total of 841 players (mean age, 13.7 +/- 0.9 years) participated; 11% reported serious overuse injury in the previous year, and 64% participated in other sports before the age of 12 years. Players who participated in other sports at <12 years old (OR, 1.79; 95% CI, 1.09-2.94; P = 0.02) and those who trained for more weekly hours than their age in fifth to sixth grade (OR, 1.70; 95% CI, 1.07-2.72; P = 0.03) had greater odds of reporting serious overuse injuries. Conclusion: Multisport athletes and high training volume in fifth-sixth grade were associated with previous serious overuse injuries. Clinical Relevance: Coaches and parents of male youth soccer players should be aware of the increased risk of serious overuse injury participating in multiple sports simultaneously, and youth athletes should adhere to age-appropriate volume recommendations.