Maarten van Egmond

11 General introduction 1 GENERAL INTRODUCTION Major thoracic and abdominal surgery is associated with a high risk of postoperative complications and a delayed functional recovery. 1-3 Physiotherapists play an important role in improving the patients’ physical functioning before and immediately after surgery to enhance postoperative recovery. 3,4 In recent years, there has been increasing evidence that preoperative physical functioning is associated with postoperative outcomes. Research has illustrated that improving preoperative muscle strength and cardiorespiratory fitness leads to a shorter length of stay in patients treated with oncological abdominal surgery, less postoperative pulmonary complications in patients treated with coronary artery bypass graft surgery and increased postoperative cardiorespiratory fitness levels in patients treated with oncological pulmonary surgery. 3,5,6 As a result, preoperative physiotherapeutic interventions are most commonly performed in different surgical populations to improve preoperative physical functioning, also known as prehabilitation , in order to reduce the risk of poor postoperative outcomes. 2,4 The effectiveness of postoperative physiotherapy has also been well documented in several populations. It has been shown that high-intensity training for patients after lung cancer surgery, leads to improved muscle strength, physical fitness and quality of life. 7 Moreover, it has been reported that early mobilization after thoracic surgery leads to a reduced length of hospital stay and improved physical functioning. 8 The effects of surgery on physical functioning Thoracic and abdominal surgery is a major stress factor that negatively affects physical functioning. 2,9,10 The surgically induced catabolic stress response increases metabolic rate to recover homeostasis. 11 This response to surgical stress is initially beneficial and the majority of patients return to their preoperative levels of physical functioning after surgery. 11 However, in patients with a poor preoperative physical functioning and low physiological reserve, the surgically induced stress response could potentially lead to severe muscle wasting, reduced cardiopulmonary function and increased risk of postoperative complications as a result of metabolic and catabolic processes, leading towards prolonged hospitalization and delayed functional recovery (Figure 1). 2,11 Despite the developments in surgery and surgical management to reduce these negative effects of surgical stress and the risk of postoperative complications, the incidence of postoperative complications and poor postoperative recovery following major abdominal and thoracic surgery remains high. 4 Besides surgery-related complications, pulmonary and