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PURPOSE: This study aimed to examine changes in physical activity among children and adolescents, by race/ethnicity, in the United States from 2003-2004 to 2005-2006. METHODS: Secondary analysis of the objectively measured accelerometer data among children and adolescents 6-19 yr: 2003-2004 (n = 1665) and 2005-2006 (n = 1716) from the nationally representative National Health and Nutrition Examination Survey 2003-2004 and 2005-2006. We estimated regression coefficients for change between the two periods by age group, accounting for sampling design and adjusting for age, sex, race/ethnicity, and number of hours monitored. We tested for differences in mean accelerometer counts per minute and minutes per day of moderate and vigorous physical activity trends by race/ethnicity and gender. RESULTS: Physical activity decreased with age, boys were more active than girls, and non-Hispanic black children were more active than non-Hispanic whites (all P < 0.01). Overall mean accelerometer counts increased from 2003-2004 to 2005-2006 for children ages 6-11 yr (+31.6 counts per minute; 95% confidence interval = 0.51-62.6) but not among adolescents ages 12-19 yr. There was an increase over time in mean accelerometer counts among 6- to 11-yr-old non-Hispanic white children (+52.4 counts per minute, P = 0.007; 95% confidence interval = 15.7-89) but a decrease among non-Hispanic black and Mexican American children. No changes over the period in moderate and vigorous physical activity were found in either age group. CONCLUSIONS: The lack of improvement in physical activity among all children and adolescents and a potentially emerging race-ethnic disparity indicate a need for further research on potential mechanisms underlying these differences. Effective interventions to improve physical activity opportunities and attenuate the decline in activity levels as children enter adolescence are needed.
Gortmaker et al. (Thu,) studied this question.