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

Purpose: To investigate whether Finnish adolescents' cardiorespiratory fitness measured using the 20 m shuttle run test (20mSRT) changed between 1995 and 2020 and to examine between-group variation in the five datasets during the past 25 years. Methods: Data on five cohorts were collected in 1995 (n = 498), 1998 (n = 796), 2003 (n = 2383), 2010 (n = 1383), and 2020 (n = 719). The 20mSRT was administered, following the exact same protocol, to all cohorts. A general linear contrast model was used to examine cohort differences in the 20mSRT scores. Variation across cohorts was tested using chi-square-based between-group tests. Results: Girls' 20mSRT scores decreased from 1995 to 2010 and remained stable from 2010 to 2020. Boys' 20mSRT scores decreased continuously from 1995 to 2020. In addition, the variation in girls' 20mSRT scores was larger in the 2020 than 2003 cohort, indicating the growth of SRT differences between individuals in 2020 cohort compared to 2003 cohort. Similarly, boys' scores showed greater variation, especially in the 2010 and 2020 cohorts than in the 1998 cohort. Conclusion: 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.