Results: The proportion of respondents who indicated a “high” level of specialization increased with age, and there were significant differences among the age groups, except between junior high school and high school. The proportion of those active for >8 months in a year also increased with age, with over95 % of junior high and high school students being active for >8 months in a year. Prevalence of acute injuries increased with increasing specialization in all age groups, and for overuse injuries, it was prominent among students in grades 1‒3, 4‒6 and high school.