Disparities in youth physical activity in the United States: 2003-2006.

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.