Modeling energy expenditure and oxygen consumption in human exposure models: accounting for fatigue and EPOC

Abstract

Human exposure and dose models often require a quantification of oxygen consumption for a simulated individual. Oxygen consumption is dependent on the modeled individual's physical activity level as described in an activity diary. Activity level is quantified via standardized values of metabolic equivalents of work (METS) for the activity being performed and converted into activity-specific oxygen consumption estimates. However, oxygen consumption remains elevated after a moderate-or high-intensity activity is completed. This effect, which is termed excess post-exercise oxygen consumption (EPOC), requires upward adjustment of the METS estimates that follow high-energy expenditure events, to model subsequent increased ventilation and intake dose rates. In addition, since an individual's capacity for work decreases during extended activity, methods are also required to adjust downward those METS estimates that exceed physiologically realistic limits over time. A unified method for simultaneously performing these adjustments is developed. The method simulates a cumulative oxygen deficit for each individual and uses it to impose appropriate time-dependent reductions in the METS time series and additions for EPOC. The relationships between the oxygen deficit and METS limits are nonlinear and are derived from published data on work capacity and oxygen consumption. These modifications result in improved modeling of ventilation patterns, and should improve intake dose estimates associated with exposure to airborne environmental contaminants.

Changes in oxygen uptake kinetics after exercise caused by differences in loading pattern and exercise intensity

“…Isaacs et al . reported that the O 2 deficit from the beginning of exercise to the steady state phase affects to the fast component, whereas the O 2 deficit engendered above AT affects the slow component.…”

Design of a Charge-Sustaining Energy Management System for a Free-Floating Electric Shared Bicycle

“…The assessment of cycling effort and cyclist fatigue are extensively addressed in literature and involve many different aspect of human physiology (see for example [19]- [23] [19], [24], [25]). The most accurate method requires the measurement of the instantaneous flow of O 2 and blood lactate.…”

Demand or supply for schooling in rural India?

“…This feature may be very helpful for accomplishing exposure modeling studies designed for maintaining proper intra-and inter-individual correlations (Glen et al, 2008). Such studies are extremely useful for understanding the relationship between intraindividual variability and inter-individual variability in exposure analyses (Frazier et al, 2008;Isaacs et al, 2008Isaacs et al, , 2012Xue et al, 2006).…”