Quantifying energy expenditure and physical activity in the context of dose response

Purpose: Methods for assessing physical activity (PA) and energy expenditur e (EE) were reviewed to identify potential limitations to evaluating and in terpreting dose-response relationships between PA and health-related outcom es and to suggest future research directions in this area. Methods: Literat ure describing PA and EE assessment methodology was reviewed according to t he reported validity, reliability, and feasibility of the measurement in ep idemiologic studies. A summary of this review is presented for techniques a pplicable to studying PA or EE among free-living individuals. Results: Seve ral methods with varying degrees of precision and feasibility have been use d to assess PA and EE in free-living populations. Lack of a gold standard f ield measure of PA may explain some of the variability in precision among t hese methods;. The most accurate field measure of EE appears to be doubly l abeled water; however, this approach has limited feasibility in terms ol: c ost and use in studies of total EE only. Electronic motion sensors and phys iologic measures related with EE are limited in their ability to discrimina te specific types of PA and by inconvenient measurement procedures. Self-re ported PA records and surveys are low cost, relatively unobtrusive methods of assessing PA and EE in field settings and vary in terms of their format, mode of administration, and degree of detailing habitual PA levels. Dispar ity in the metric used to quantify PA and EE exists within the current lite rature, which limits the interpretation and comparison of observed dose-res ponse relationships. Conclusions: Efforts to develop equated methods of ass essing PA and EE in free-living populations are needed before a systematic evaluation and interpretation of dose-response characteristics between PA a nd specific health-related parameters can be undertaken.