Risk assessment
Functional capacity (METs)
Also known as: METs, metabolic equivalents, exercise tolerance
Functional capacity describes how much physical activity a patient can perform, measured in metabolic equivalents (METs). One MET is resting oxygen consumption. Four METs — climbing a flight of stairs or walking up a hill — is the usual threshold below which perioperative guidelines suggest further cardiac assessment before non-cardiac surgery.
- Unit
- MET — metabolic equivalent of task
- 1 MET
- Resting oxygen consumption (~3.5 mL/kg/min)
- Key threshold
- 4 METs
- Below 4 METs
- Poor functional capacity — consider further cardiac assessment
What the numbers mean
| METs | Typical activity |
|---|---|
| 1 | Eating, dressing, working at a computer |
| 2–3 | Walking indoors, walking 100m on level ground |
| 4 | Climbing a flight of stairs, walking up a hill, light housework |
| 5–9 | Running a short distance, heavy housework, moderate cycling |
| 10+ | Strenuous sport — swimming, singles tennis, football |
Why it is hard to capture
Functional capacity is one of the most predictive and least reliably recorded pieces of pre-operative information, because it depends entirely on the question being asked well. “How is your exercise tolerance?” invites “fine” from a patient who has not climbed a flight of stairs in two years. The useful question is concrete and activity-anchored: can you walk up a flight of stairs without stopping?
A structured interview asks it that way every time, which is why functional capacity and frailty is one of the 12 domains Socrates Pre-Op covers rather than a free-text field someone fills in at the clinic.