Survivors of critical illness suffer a range of physical, psychological and social problems known together as the post-ICU syndrome. Physical weakness is common, long lasting, and interferes with quality of life for many ICU survivors. Physical weakness observed close to the time of ICU discharge is likely be caused by the disordered physiology and immobility associated with critical illness. These factors may be less important in the long term, where pre-existing frailty may be more important. A large number of trials have tested physical interventions (exercise, passive and active mobilisation, and neuromuscular electrical stimulation) delivered during and after critical illness. At this time, the evidence suggests that early mobilisation can improve important short term outcomes (such as length of stay, duration of mechanical ventilation, functional independence, and mobility), but have not been shown to affect long term outcomes. No physical interventions delivered after ICU discharge has demonstrated effectiveness. This article describes the physical problems experienced by ICU survivors, and provides an up to date review of critical care physical intervention trials.