Increasing focus on the negative effects of bed rest have become more apparent in the intensive care unit within the last decade. A few studies have found an association between early rehabilitation starting at the intensive care unit and outcome after discharge from rehabilitation. The early mobilization presents with challenges regarding haemodynamic stability. The aim of this trial is to assess the feasibility before conducting a larger randomised trial that will investigate benefits and harms of an intensive physical rehabilitation intervention focusing on mobilisation to the upright position, starting as early as clinically feasible in the intensive care unit