- Overview
- Metabolic equivalents (METs) are a standardized way to measure exercise intensity and energy expenditure.
- One MET represents the amount of oxygen consumed at rest
- METs increase with higher activity levels.
- Definition of METs
- 1 MET = 3.5 mL O₂/kg/min
- This is the amount of oxygen consumed per kilogram of body weight per minute at rest.
- Exercise capacity is often reported in METs, making it easier to compare across different populations.
- METs and Cardiopulmonary Exercise Testing (CPEX)
- A. VO₂ Max and METs Conversion
- 1 MET = 3.5 mL O₂/kg/min
- VO₂ max (mL/kg/min) ÷ 3.5 = Peak METs Achieved
- For example
- If a patient has a VO₂ max of 35 mL/kg/min, then:
- 35 ÷ 3.5 = 10 METs
- For example
- METs as a Measure of Functional Capacity
- METs provide a simple way to assess exercise tolerance in clinical and perioperative settings.
- Higher METs correlate with better cardiovascular fitness.
- Low METs indicate impaired aerobic capacity (e.g., heart failure, pulmonary disease).
- METs and Perioperative Risk Stratification
- In preoperative assessment, METs are used to predict surgical risk based on functional capacity.
- Functional Capacity and Surgical Risk
- METs Achieved Functional Status Surgical Risk
-
10 METs Excellent fitness Low risk for most surgeries
-
4–10 METs Moderate fitness Generally safe for major surgery
- <4 METs Poor fitness High surgical risk; further evaluation needed
- ≥4 METs is often considered the threshold for safe surgery.
- If a patient cannot achieve 4 METs, additional CPEX testing, cardiac stress tests, or prehabilitation may be needed.
- Estimating METs Clinically (Without CPEX)
- Functional capacity can be estimated based on patient-reported activities:
- Activity - Approximate METs
- Sitting quietly - 1 MET
- Walking slowly (~2 km/h) - 2 METs
- Climbing a flight of stairs - 4–5 METs
- Brisk walking (~6 km/h) - 6 METs
- Jogging (~8 km/h) - 8 METs
- Running (~10 km/h) - 10 METs
- Competitive sports (e.g., soccer) - 12–15 METs
- If a patient cannot walk up a flight of stairs or carry groceries, they likely have low METs (<4) and may need further evaluation.
- Functional capacity can be estimated based on patient-reported activities: