A full pre-operative anaesthetic assessment will be performed for each participant, and this is part of the standard treatment that they receive if they are patients scheduled for abdominal surgery. Participants will be categorised as either fit or unfit, by means of the Duke Activity Survey, initial cardiopulmonary exercise testing (CPET), and a modified frailty index. CPET will be performed on an electromagnetically braked ergometer using individualised stepped protocols based on the individua