 Neoadjuvant chemotherapy NAC prior to surgery for upper gastrointestinal oesophageal and gastric cancer is associated with improved survival. The investigators propose a prospective blinded observational cohort study of patients undergoing NAC prior to elective upper gastrointestinal cancer resection oesophagectomy and gastrectomy in three NHS teaching hospitals. The investigators have pilot data showing that NAC reduces objectively measured exercise capacity fitness. The literature suggests that a lower level of exercise capacity is associated with a high risk of adverse outcome death and serious complications after major surgery. 