NBME Surgery Shelf Practice Test

METs gauge how much energy the body uses during activity and serve as a practical measure of functional capacity in preoperative evaluation. Four METs roughly correspond to brisk walking, climbing a flight of stairs, or light cycling—activities most people can perform without symptoms. In surgical risk assessment, having a functional capacity of at least four METs is considered adequate, because it indicates sufficient physiologic reserve and is associated with a lower perioperative cardiac risk. If a patient can only perform activities under four METs, they may have limited cardiac reserve and could need further testing or optimization before surgery. Activities around six or eight METs show even greater exercise tolerance, but the threshold used to define adequacy is four METs. This is why four METs is the best-cutoff choice.