Physical Activity Measured by Accelerometers in the National Health and Nutrition Examination Survey

Purpose To describe physical activity of a nationally representative sample of the United States population as measured by the Actigraph accelerometer.

Methods Data were collected from 6830 participants of NHANES 2003-4 ages 6+ years. Participants were requested to wear the monitor for 7 days during waking hours.

Results Approximately 74% of participants wore the monitor for at least 10 hours on 4-7 days. Compliance was lowest in adolescents (age 12-19 y, 59%) and highest in the elderly (60+ y, 87%), similar in men (75%) and women (74%), and somewhat lower in non-Hispanic blacks (64%). Mean accelerometer counts/day as well as time spent above count thresholds selected to indicate moderate and vigorous intensity activity will be presented for age, gender, and race-ethnicity groups.

Conclusions Accelerometers remove error in physical activity assessment due to difficulty in recall and desirability bias. However, they do not provide complete measures of physical activity or energy expenditure. Analysis of this data set also presents some challenges because of its size (>70,000,000 records) and the paucity of information concerning count thresholds for activity levels, particularly in the elderly. Nevertheless, objective data on physical activity in a nationally representative sample provide valuable insights into behavior.