The purposes of this project are to find optimal methods of assessing physical activity energy expenditure (PAEE) in a free-living condition and to use these methods to determine the impacts of physical activity frequency, duration, and intensity on health. We previously collected data, using a variety of accelerometers, heart rate monitors, and pedometers, through which we proposed to estimate PAEE in a cohort of healthy young adults. We simultaneously collected laboratory, nutrition, and anthropometric data from the same cohort. During this year we have worked with the listed collaborators to develop methods to analyze these data. We are currently designing protocols in which we will expand the use of several PAEE monitors to better understand the relative impacts of PAEE on preventing metabolic diseases and their complications.