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PHYSICAL ACTIVITY INDEX FOR CHILDREN: A COMPARISON OF LITERATURE VALUES AND EPA'S CHAD
SMITH, L., L. LIAO, K. ISAACS, T. R. MCCURDY, AND J. XUE. PHYSICAL ACTIVITY INDEX FOR CHILDREN: A COMPARISON OF LITERATURE VALUES AND EPA'S CHAD. Presented at International Society of Exposure Analysis Conference, Tucson, AZ, October 30 - November 03, 2005.
The two main objectives of this research are (1) to improve and update and (2) to analyze the CHAD database.
For objective 1, we will
* Reconfigure the CHAD program into a completely modularized Oracle database.
* Redesign User Interface for effcient utilization of the program's capability.
* Obtain dates for those surveys that did not provide them to us, so that we can obtain associated meteorological/climatic inputs for the person-days of information without them.
* Revise the upper and lower bound delimiters in the energy expenditure distributions used for activity-specific estimates.
For objective 2, we will
* Evaluate data quality.
* Evaluate trends and activities for various subgroups.
* Identify temporal patterns for longitudinal data.
* Characterize resolution required for output for exposure and dose models.
The physical activity index (PAI) is a measure of an individual's energy expenditure level (and thus oxygen consumption) calculated as a time-weighted average of metabolic equivalents (METS) over the individual's activities. Many exposure models rely upon EPA's CHAD data base to obtain activity patterns. The object of this study was to compare PAI values reported in the literature to those calculated from CHAD.
From the literature, 44 studies involving girls and 38 involving boys were used. From each study, the mean and standard deviation of PAI, sample size, and age were available. Ages ranged from 0 to 17. The summary statistics were averaged, weighted by sample size, to obtain a mean and standard deviation for each age-gender category. For these same categories, PAI values were calculated from CHAD, adjusting for both physiological limits and excess post-exercise oxygen consumption.
Data were examined both graphically and via statistical hypothesis testing. The results indicate that CHAD yields higher PAI values than those reported in the literature for both genders across the range of ages. While variability of PAI was not significantly different between CHAD and the literature studies when tested across all ages, the results suggest that CHAD may give larger standard deviations for older children.