Multiple stakeholders, including anesthesiologists and patients, have identified improving the outcomes of older patients and preoperative exercise training (prehabilitation) as 2 of the 10 most important areas for future perioperative research. Physical vulnerability is an important aspect of the frailty syndrome, and may be amenable to structured exercise therapy. However, the evidence for preoperative exercise training (prehabilitation) improving postoperative outcomes is obscured by methodological limitations and a focus on non-elderly patients. Recently, evidence has emerged that older and sicker patients may benefit most from prehab, however, this hypothesis has not been formally tested.