IMPORTANCE Physical activity in youth is associated with adult health. Understanding the prevalence and factors of moderate to vigorous physical activity among adolescents and young adults will guide public health and policy efforts. OBJECTIVES To describe the current patterns of physical activity and duration among adolescents and young adults and to identify the direction and magnitude of associations between physical activity and income, race/ethnicity, and sex. DESIGN, SETTING, AND PARTICIPANTS This cross-sectional secondary data analysis used the self-reported physical activity data of adolescents and young adults from the National Health and Nutrition Examination Survey from 2007 through 2016. This data set is a multistage probability sample of the noninstitutionalized US population and allows estimates that represent the US population. The years 2007 through 2016 were selected because of the consistent physical activity questions during this period. Adolescents and young adults aged 12 to 29 years who responded to the survey were included. Individuals who were underweight were excluded. Data analysis was performed from October 17, 2017, to April 27, 2018. MAIN OUTCOMES AND MEASURES Self-reported physical activity duration and intensity. RESULTS Of the 9472 participants, 4771 (50.4%) were males, and the weighted mean age (range) was 20.6 (12-19) years. Across all demographic categories, females reported less physical activity than did their male counterparts. White adolescent males were most likely (89.3%; 95% CI, 86.5%-92.1%) and black females aged 18 to 24 years were least likely (45%; 95% CI, 39.0%-51.0%) to report any physical activity. Among those who were active, black males aged 18 to 24 years reported the longest duration of activity (77.9 minutes per day; 95% CI, 66.4-89.3 minutes per day), and black females aged 25 to 29 years reported the shortest duration of activity (33.2 minutes per day; 95% CI, 28.1-38.2 minutes per day). In adjusted models, younger age, white race, and higher income were associated with greater physical activity. CONCLUSIONS AND RELEVANCE Female adolescents and young adults were not meeting the recommended guidelines for physical activity, and substantial disparities by race and income levels were noted. These data highlight opportunities for targeted physical activity programming and policy efforts.

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