Abstract
The concept of fatigue has entered medicine from other disciplines in which the term refers to weakening of a material by demands put upon it. Its application to the behavioural and subjective changes that characterize postoperative convalescence has led to the assumption that these changes reflect the physiological and metabolic consequences of surgery. Because evidence does not support this view, we outline a new theory in which postoperative fatigue is the product of physiological, psychological and cultural factors. This theory leads to novel predictions that can be tested in future clinical research. Of particular interest will be the evaluation of systematic attempts to change patient and staff expectations about postoperative convalescence.