Functional capacity has been shown to be a major determinant of surgical outcome since it is related to postoperative complications, activity and daily function, level of independence and quality of life. Anesthesiologists as "perioperative physicians", can identify those scoring systems that assess functional capacity, whether from the basic physical history and walk test to the most complex such as cardiopulmonary exercise testing, and formulate intraoperative and postoperative interventions (rehabilitation) to minimize the impact of surgery on the recovery process. Nevertheless, the preoperative period can be used as an opportune time to increase functional reserve in anticipation of surgery, thus enabling the patient to better withstand the metabolic cost of surgical stress (prehabilitation). There is a compelling evidence that prehabilitation programs, including physical exercise, nutritional optimization and relaxation strategies, can enhance preoperative physiological reserve, however further studies are needed to identify the most appropriate protocols for those patients at risk, and assess the impact of such programs on clinically meaningful surgical outcomes.