Accelerometer-determined steps per day in US adults.
BACKGROUND
The 2005-2006 National Health and Nutrition Examination Survey (NHANES) released, for the first time, the ActiGraph AM-7164 accelerometer-defined step data in addition to time in intensity (defined by activity counts). This accelerometer is known to have a lower sensitivity threshold than accepted pedometers, leading to relatively higher step estimates.


OBJECTIVE
The purpose of this analysis is to provide the population- and sex-specific epidemiology of accelerometer-determined steps per day with and without censoring steps detected at the lowest end of the activity spectrum (i.e., inactivity).


METHODS
The analysis sample represents 3744 participants > or =20 yr who had at least one valid day (i.e., at least 10 h) of monitoring. Means (SE) for steps per day were computed using all steps (i.e., uncensored) and again after censoring those steps taken at an intensity <500 activity counts per minute (indicative of inactivity intensity).


RESULTS
On average, US adults took 9676 +/- 107 uncensored steps per day or 6540 +/- 106 censored steps per day.


CONCLUSIONS
The results of this nationally representative survey indicate that US adults take approximately 10,000 uncensored accelerometer-determined steps per day, which is improbable considering other studies of free-living physical activity in the United States. Until a more valid conversion factor is ascertained for translating accelerometer and pedometer-determined steps, our use of the <500 activity count per minute threshold holds considerable merit.
Tudor-Locke
Catrine
C
Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA. Tudor-Locke@pbrc.edu
Johnson
William D
WD
Katzmarzyk
Peter T
PT
D000054:Acceleration; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D016001:Confidence Intervals; D003625:Data Collection; D005260:Female; D015438:Health Behavior; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity; D009749:Nutrition Surveys; D014481:United States; D016138:Walking / Q000502:physiology*