RESUMEN
OBJECTIVES: The aim of this study was to analyze the temporal trends in cardiorespiratory fitness (CRF) and body mass index (BMI) among children and adolescents from 1985 to 2019. METHODS: A total of 1 840 212 children and adolescents aged 7-18 years (921 223 boys) were tested for CRF from 1985 to 2019. CRF was tested by 50-m × 8 shuttle run for boys and girls aged 7-12 years, 1000-m run for boys aged 13-18 years, and 800-m run for girls aged 13-18 years. Trends in BMI from 2000 to 2019 were also investigated. RESULTS: Cardiorespiratory fitness decreased during the entire 34 years among children and adolescents in all sex and age categories, and the most rapid decline occurred from 1995 to 2005. Some positive trends in CRF were observed among adolescents aged 13-15 years from 2005 to 2019 and among girls aged 16-18 years from 2014 to 2019. The variation in the CRF distribution was not uniform, with Z-scores for participants with high CRF levels changing little or increasing (CRF stabilized or improved) and Z-scores for participants with low CRF levels continuing to decrease (CRF decreased). BMI increased over time for boys and girls in all age categories, with an acceleration of the increase for adolescents in recent years. CONCLUSIONS: This study revealed that the overall CRF levels of Chinese children and adolescents decreased over three decades but stabilized or improved in recent years. BMI continued to increase. Our findings are important for the focus on future domestic physical fitness and public health.