Population-based trends and distributional characteristics in sit-ups performance among school-aged girls in urban China over three decades.

This paper aims to assess population-based trends and distributional characteristics in the sit-ups performance, body height, body mass and body mass index (BMI) among school-aged girls in urban China from 1985 to 2019. Height, mass, BMI and sit-ups performance data for Han Chinese urban girls aged 7-18 years were obtained from the Chinese National Surveillance on Students' Constitution and Health surveys from 1985 to 2019. Population-based trends were estimated by a post-stratification population weighting procedure. There was a moderate improvement in sit-ups performance from 1985 to 2019, increasing by 25.7% or 0.69 effect size (ES). Girls aged 10-12 years experienced the smallest improvement (0.46 ES) and girls aged 16-18 years experienced the largest improvement (0.88 ES). Improvements in sit-ups performance were the major trend across periods, but there was a negligible improvement in the 1990s (0.04 ES) and a small decrease in the 2000s (-0.36 ES), while height, mass and BMI (from 2000 to 2019) continued to increase from 1985 to 2019. The distribution of the change in sit-ups performance was uneven, the improvements were somewhat greater at both ends of the distribution.The government should implement differentiated health promotion programs, especially for those with greater health risks.