Impaired cardiorespiratory fitness (CRF) is associated with poor post-operative outcome following major surgery (Moran et al., 2016). Given its importance, approximately 30,000 preoperative cardiopulmonary exercise tests (CPET) are conducted in the UK each year to assess patient risk and plan care (Levett et al, 2018). Exercise training can improve CRF prior to surgery (West et al. 2015), however the current evidence base is lacking. Thus, we conducted a clinical case study to address feasibility and benefits of high intensity interval training (HIIT). A 70 year-old female who underwent an oesophagectomy for oesophageal cancer developed ischaemia of the gastric conduit and was left with a pharyngostomy, and feeding jejunostomy. Further surgery for restoration of the upper gastrointestinal tract with a colonic interposition was considered, however the patient’s fitness for surgery was stratified as high-risk. The medical history also included a myocardial infarction and coronary artery bypass graft. Following CPET to determine baseline fitness, a 10-week supervised HIIT intervention was conducted. Three exercise sessions of 40 minutes duration separated by 48 hours recovery were completed each week using cycle ergometry. Sessions comprised six, two-minute bouts of heavy exercise (50% difference between power output at peak exercise and anaerobic threshold (AT)) interspersed by three minutes of moderate exercise (80% power at AT) based on previous research (West et al. 2015). Heart rate (12-lead ECG) and blood pressure was monitored during exercise. A CPET was conducted every two weeks and HIIT intensity adjusted accordingly. The HIIT intervention was well tolerated with no adverse events occurring, and 29 of 30 sessions completed. After 10 weeks, pulmonary oxygen uptake at peak exercise and AT increased by 36 and 27% respectively (18.6 vs 13.7 and 10.5 vs 8.3 ml.kg-1.min-1) and traversed a fitness stratification threshold of 15 ml.kg-1.min-1 for peak oxygen uptake. The patient was referred for surgery. Despite the high intensity exercise, HIIT proved feasible, safe, and well tolerated. Impressive cardiopulmonary adaptation occurred in excess of variation typical of repeated measures (Rose et al., 2018). Improved CRF over a short period of time enabled the patient to be classified as “fit” for surgery, and thus supports investigating HIIT in future trials as an adjunct prior to major surgery.