The MOSAIC observational study will measure activity in critically ill patients for up to 28 days in the hospital using two different, objective measures, a clinical mobility scale and accelerometry. We will evaluate the independent association between activity and outcomes 3 and 12 months after ICU discharge. Specifically, Aim 1 will determine the relationship between activity and disability in ADLs and mobility. Aim 2a will determine the relationship between activity and physical and cognitive function. Aim 2b will evaluate physical and cognitive function as mediators of long-term disability. Aim 3a will determine the relationship between activity and biomarkers of inflammation and coagulation. Aim 3b will determine the relationship between these biomarkers of inflammation and coagulation and disability, physical and cognitive function.