# Functional capacity (METs)

> 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.

*Source: https://getpathways.ai/glossary/functional-capacity-mets*

Also known as: METs, metabolic equivalents, exercise tolerance

- **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.