This study examines changes in physical activity using accelerometer data from a youth population and discusses differences in these changes by age, gender, and race/ethnicity.

Analysis of four years of data, completed in two waves (2003–2004 [n=1,665] and 2005–2006 [n=1,716]), was used to measure activity levels of non-Hispanic White, non-Hispanic Black, and Mexican American children and adolescents. Two age categories were defined: ages 6 to 11 and ages 12 to 19 to keep the results comparable to previous National Health and Nutrition Examination Survey studies. Accelerometers were instructed to be worn for seven days to capture minute-to-minute physical movement.

Key Points:

• Physical activity decreased with age, boys were more active than girls, and mean accelerometer counts increased over the four years for 6- to 11-year-old non-Hispanic White children but decreased among non-Hispanic Black and Mexican American children.
• Non-Hispanic Black children were more active than non-Hispanic White children.

Limitations of this study include: using cross-sectional samples that do not follow the same children over time; accelerometers do not record upper body movements or activity performed while swimming; and data did not account for any children with disabilities. This data shows the need for increased physical activity as children enter adolescence, and the emergence of a potential race-ethnic disparity in youth physical activity.