Accelerometer-determined steps per day in US children and youth

Abstract

Purpose: The 2005–2006 National Health and Nutrition Examination Survey collected accelerometer-defined step data in addition to activity counts. The accelerometer used (ActiGraph AM-7164) is known to detect more low-force steps than research-quality pedometers. This study extends similar research focused on adults in National Health and Nutrition Examination Survey. Its purpose is to provide the descriptive epidemiology of accelerometer-determined steps per day in US children (6–11 yr) and youth (12–19 yr), with and without censoring steps detected at G500 activity counts per minute, in an attempt to interpret these data against existing pedometer-based scales.

Methods: The analysis sample represents 2610 children and youth 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 detected steps (i.e., uncensored) and again after disregarding those steps below 500 activity counts per minute (i.e., censored).

Results: US children average approximately 13,000 (boys) and 12,000 (girls) uncensored accelerometer-determined steps per day. Comparable values for male and female youth are 11,000 and 9000 uncensored accelerometer-determined steps per day, respectively. Censoring low-force steps reduces uncensored values by approximately 2600 steps per day overall, shifts distributions to the left, and shows that almost 42% of US male children and almost 21% of female children are sedentary as interpreted against expected values for steps per day in childhood using a pedometer-based scale.

Conclusions: Regardless of censoring or not, across age, the US data show a peak value at 6 yr followed by generally consistent declines in steps per day values throughout childhood and into youth.