Measurement of physical activity, and in recent years, sedentary time are a cornerstone of epidemiological and intervention studies aimed at promoting physical activity behavior. These interventions can significantly impact not only physical activity behavior but also a variety of health outcomes. Researchers often use a combination of measures including subjective as well as objective assessments that will provide a valid and reliable snapshot of the population. In this session we present 3 studies that have sought to accurately assess physical activity and sedentary time among middle aged and older adults with the larger goal of examining activity behaviors and their associations with health outcomes. In the first presentation, Dr. Erlenbach will present the association between actigraph and self-reported physical activity and sedentary time in a population of adults in USA. In the second presentation, Dr. Elavsky will present data from 12-month prospective monitoring via Fitbit and physical activity questionnaires in a population of inactive and active residents of the Czech Republic. In the third presentation, Dr. Collins will present associations between ActiGraph and self-reported physical activity, and their relation to an outcome of brain health, in a sample of older adults in the United States. Finally Dr. Rosenberg will collectively discuss the similarities and differences across the 3 presentations and place them in the context of physical activity epidemiology and the role of measurement in identifying and associating physical activity with improvements in health outcomes.
