The purpose of this study is to test if a 6-week programme of exercise improves physical function and health related quality of life in patients following intensive care who are discharged from hospital. In this study the investigators will compare the physical function and health related quality of life of patients who attend the programme with patients who do not. The 6 week exercise programme will be run by physiotherapy staff, and will mostly take place in a hospital gym. The investigators will measure patients' physical function, exercise capacity, level of breathlessness and their quality of life before and after the 6-week programme, and 6 months later. The investigators will also interview patients to ask their views about the acceptability, enjoyment and satisfaction with the exercise programme. If this study shows that the physical function and health related quality of life are improved in those who took part in the exercise programme, then it will provide useful information which will help the development of services for patients after critical illness. The results will also provide information which will help us design future clinical trials for this patient population.