The association between a body shape index and cardiorespiratory fitness among adolescents in rural China: a sex-specific cross-sectional study

BackgroundCardiorespiratory fitness (CRF) among Chinese adolescents has been declining year by year, with the decline being particularly pronounced in rural areas. As a novel indicator of body composition, the a body shape index (ABSI) has rarely been examined in previous studies regarding its association with CRF among adolescents in rural areas. This study aims to guide the improvement and enhancement of CRF among adolescents in rural China.MethodsUsing a stratified random cluster sampling method, we conducted a cross-sectional assessment of height, weight, waist circumference, and 20-m shuttle run test (20-m SRT) performance among 18,948 adolescents aged 6–17 years in rural areas of China. We analyzed the association between ABSI and 20-meters SRT using methods such as one-way analysis of variance (ANOVA) and linear regression analysis.ResultsAmong adolescents aged 6–17 years in rural China, the ABSI was (0.069 ± 0.013) and the 20-m SRT was (29.69 ± 17.16) laps. Overall, there were statistically significant differences in the interquartile ranges of the 20-m SRT across the 6–8, 9–11, 12–14, and 15–17 age groups (F = 33.841, 14.916, 13.858, 7.715; P < 0.001). Curvilinear regression analysis showed an inverted U-shaped relationship between ABSI and 20-m SRT. Overall, in the 6–8 years, 9–11 years, 12–14 years, and 15–17 years age groups, the 20-m SRT was highest when the ABSI was 0.056, 0.070, 0.094, and 0.054, respectively, reaching 18.673, 26.226, 38.328, and 40.499 laps, respectively.ConclusionsThere is an inverted U-shaped relationship between ABSI and 20-meter SRT among adolescents in rural China. Maintaining a reasonable ABSI may on CRF.