Key PointsQuestionWhat is the evidence for the efficacy of preoperative high-intensity interval training (HIIT) in improving cardiorespiratory fitness and surgical outcomes?FindingsThis systematic review and meta-analysis of 12 studies including 832 patients assessed the association of preoperative HIIT with either cardiorespiratory fitness or postoperative outcomes. There was evidence that HIIT is significantly associated with increased preoperative cardiorespiratory fitness and reduced postoperative complications.MeaningThese findings suggest that preoperative HIIT may improve cardiorespiratory fitness and reduce postoperative complications.