Secular trends in 20 m shuttle run test performance of 14- to 15-year-old adolescents from 1995 to 2020.

The results of this study showed an overall decline in the cardiorespiratory fitness performance measured by 20mSRT of Finnish adolescents. Boys' scores decreased continuously from 1995 to 2020, whereas girls' scores remained stable after 2010. Examination of the variation in scores further revealed that the gap in scores between the adolescents with the highest and lowest scores increased over time.