Disparities in physical fitness of 6-11-year-old children: The 2012 NHANES National Youth Fitness Survey

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© 2020 The Author(s). Background: Children's physical fitness is an important predictor of metabolic health, physical function, and academic achievement. Although fitness is determined partially by heritable factors, it can be maintained and improved through regular physical activity. Because physical activity is known to vary by socioeconomic status, physical fitness may be expected to vary similarly. With this in mind, the purpose of this study was to examine disparities in physical fitness performance among a nationally-representative sample of 6-11 year-old children living in the United States. Methods: We conducted secondary analysis of physical fitness data of children ages 6-11 years (n = 686) from the nationally representative National Health and Nutrition Survey (NHANES) Youth Fitness Survey (NNYFS) 2012. We estimated sex-stratified weighted means of four fitness performance tests: cardiorespiratory endurance, upper-, lower-, and core-muscular strength. The weighted mean for each fitness assessment was compared by income groups (federal income to poverty ratio - FIPR) accounting for complex sampling design and adjusting for age. Results: Income disparities in physical fitness performance were evident among girls but not among boys. Girls from lower income groups (< 130% FIPR and 130-349% FIPR groups) showed significantly lower cardiorespiratory endurance and core muscle strength compared to those from the highest income group (≥ 350% FIPR). Conclusion: These findings highlight the need to support health-promoting physical activity among girls from disadvantaged backgrounds prior to the adolescent period.