Patients' ability to tolerate surgery is associated with physical fitness: less fit patients have an increased rate of death and serious complications following major surgery. Combined chemotherapy and radiotherapy (x-rays) prior to rectal cancer surgery is known as neo-adjuvant chemoradiotherapy (NACRT) and is associated with improved cancer removal but adversely affects physical fitness. In Liverpool, the investigators have pre-pilot data showing that NACRT reduces objectively measured physical fitness (measured by cardiopulmonary exercise testing) in patients having surgery. This pre-pilot study investigated the effects of a 6-week structured responsive endurance training programme (SRETP) after NACRT and before cancer surgery. This programme has improved both their fitness and their health related quality of life(HRQL). Now, the investigators are undertaking a randomised controlled trial to compare changes in patient's physical fitness in response to SRETP with a group of patients who will be given exercise advice. The SRETP group will exercise 3 times a week for 9 weeks. The investigators will make objective measurements of physical fitness in both groups. The investigators will monitor patient's perceptions of the training programme, HRQL, daily activity (using an accelerometer), and outcomes after surgery. The investigators believe that, patients in the exercise group will improve their physical fitness prior to surgery, change behaviour towards exercise, improve activity and HRQL following NACRT. These results will contribute to the design of a large, multi-centre trial to determine whether a SRETP increases physical fitness with a reduction in adverse outcome following surgery. The investigators will conduct an adequately powered randomized controlled trial (RCT) comparing a SRETP with 'exercise advice' in 46 rectal cancer patients. Specifically, we will test the following hypotheses and outcomes: PRIMARY HYPOTHESIS A 9-week, structured responsive endurance training programme (SRETP) compared with a control group (no training) will result in a clinically significant difference in physical fitness (2.0ml/kg/min VO2 at LT) post-NACRT prior to surgery.