Delivery of early mobilisation is feasible, safe and effective in improving both short and long-term outcomes in critically ill patients even in the early stages of recovery whilst patients remain ventilated and receiving other forms of organ support. However, the optimum 'dose' of physical rehabilitation to deliver to patients whilst in the ICU remains undetermined. Early mobilisation reflects a clinically pragmatic approach to patient management, but there are few data to support the intensity, frequency and timing of interventions.