The benefits of physical activity (PA) for health are well established. However, limited evidence is available on the relative importance of specific intensities of PA as well as sedentary time for major health outcomes. In conventional analyses, accelerometer data are collapsed into only a few intensities (e.g. light, moderate-to-vigorous).This causes substantial loss of information and limits the detection of the relative importance of specific intensities. In this project we will use a novel multivariate pattern analysis approach to describe the entire PA intensity spectrum and examine the relative importance of different PA intensities on physical and mental health and mental wellbeing.