In critically ill patients, a prolonged hospital stay, due to the initial acute insult and adverse side-effects of drug therapy, may cause severe late complications, such as muscle weakness, prolonged symptoms, mood alterations and poor health-related quality of life. The clinical aims of physical rehabilitation in both medical and surgical intensive care units (ICUs) are focussed on the patient to improve their short- and even long-term care. The purpose of this article is to review the currently available evidence on comprehensive rehabilitation programmes in critically ill patients, and describe the key components and techniques used, particularly in specialised ICUs. Despite the literature suggesting that several techniques have led to beneficial effects and that muscle training is associated with weaning success, scientific evidence is limited. Due to limitations in undertaking comparative studies in ICUs, further studies with solid clinical short- and long-term outcome measures are now welcomed.