Supervised Exercise for Post-surgery Colorectal Cancer Patients

Participants will undergo preoperative baseline screening and will be randomised to either normal postoperative care or a 12-week supervised exercise programme comprising of both an aerobic and resistance component They will be assessed prior to surgery which will include cardiopulmonary exercise testing (CPET). This is a well-established method of assessing aerobic exercise response and is widely used in the perioperative period for assessment of cancer patients with co-morbidity. The assessment days will also include: * muscle ultrasound (vastus lateralis) to ascertain muscle structure (thickness, pennation angle and fascicle length), * blood tests, * functional composite scores, * quality of life questionnaires, The assessment days will be carried out at four time points during the study; prior to surgery, before commencement of the exercise program, halfway through the intervention (6 weeks post commencement of exercise) and at the end of the study. In the week before the assessment days patients will wear a physical activity monitor to characterise their daily movements. The control group will also be assessed at the same time points and wear the activity monitors but will not take part in the exercise program. All participants will have a physical activity monitor placed onto the right thigh in the midline at postoperative day 1 until discharge or day 7, whichever is sooner. This is a non-invasive measure of activity and can discriminate between whether a patient is lying, sitting, standing or walking. Once participants self-report feeling able to start exercising again post-discharge, they will commence the 12 week programme. The intervention will consist of 2 resistance training (RET) sessions per week and 75 minutes of vigorous or 150 minutes of moderate aerobic exercise per week (can be split according to patient preference). They will receive a diary to log their sessions and will be monitored via twice weekly virtual follow-up (either telephone or v