Physical fitness status of children and adolescents in Tianjin of China during past three decades: a cross-sectional study.

Background: Significant changes in the society and lifestyle have been observed in China, which influences the physical fitness status of children and adolescents. This study aimed to estimate the physical fitness status in Tianjin during the past three decades.

Methods: Cross sectional survey was used in this study. The data were derived from the Chinese National Students' Physical Health Survey database (1985-2010) using stratified cluster randomized sampling method. A total of 58,006 subjects aged 7-21 were recruited. The ethics approval was obtained from the Ethics Committee of Tianjin Medical University before collecting data from the children and adolescents, and/or their parents/guardians on behalf of them. Also written informed consent was obtained before collecting data from the patients. The secular trend of the physical fitness status, Levels of height, weight, body mass index, and chest circumference in China were calculated. The increase velocity of according indexes were analyzed, gender and rural/urban difference were discussed afterwards. SPSS16.0 was used in the analysis.

Results: Levels of height, weight, body mass index, and chest circumference were obviously increased in 2010 compared to those levels in 1985, especially in the 9-13 age group. It was observed that the increase in the two crosses for height velocity between two genders of rural students was disappeared and the age of seven was important for the physical development.

Conclusions: The circumstance was good for the physical development of the children and adolescents. The disappearance of the two crosses for height velocity between two genders of rural students in this study might be associated with factors such as nutritional status.