Citation:

ISAACS, K., G. GLEN, T. R. MCCURDY, AND L. SMITH. CORRECTING ENERGY EXPENDITURES FOR FATIGUE AND EXCESS POST-EXERCISE OXYGEN CONSUMPTION. Presented at International Society of Exposure Analysis Conference, Tucson, AZ, October 30 - November 03, 2005.

Impact/Purpose:

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.

Description:

The EPA's human exposure and dose models often require a quantification of oxygen consumption for a simulated individual. Oxygen consumption is dependent on the individual's current level of physical activity (PA), which is determined from activity diaries selected from the Consolidated Human Activity Database (CHAD). PA is quantified via standardized values of metabolic equivalent (METS) for the activity being performed. However, it is known that oxygen consumption may remain elevated after PA is completed. This effect, which is termed excess post-exercise oxygen consumption (EPOC), requires upward adjustment of the METS values of post-PA diary activities. In addition, since an individual's capacity for work will decrease during extended PA, methods are also required to adjust diary METS values that exceed physiologically-realistic limits over time. A unified algorithm for simultaneously performing these adjustments has been developed. The method simulates a cumulative oxygen deficit for each individual and uses it to impose appropriate time-dependent reductions in METS. The relationships between the oxygen deficit and the METS limits are non-linear and were derived from published data on work capacity and oxygen consumption. Simultaneously, post-PA METS values are augmented for EPOC. These adjustments were calculated from an analysis of the current EPOC literature. The algorithm was implemented in EPA's Air Pollutants Exposure Model (APEX). The method, which is flexible and computationally efficient, resulted in (1) appropriate multi-hour METS means and (2) improved physical activity index (PAI) distributions for children.

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