Normal Oxygen Metabolic Rate in Healthy Adults
For a healthy adult at rest, the normal oxygen metabolic rate is 3.5 mL O₂/kg/min, which equals 1 MET (metabolic equivalent of task). 1
Resting Oxygen Consumption Values
Standard resting oxygen uptake is defined as 3.5 mL O₂ per kilogram of body weight per minute, which serves as the baseline (1 MET) for expressing exercise intensity 1
This value represents sitting/resting oxygen requirements in the general adult population and is used universally to calculate metabolic equivalents during physical activity 1
Age-Related Variations
Important caveat: The standard 3.5 mL O₂/kg/min value may overestimate resting metabolic rate in older adults:
In adults ≥60 years old, measured resting oxygen consumption averages 2.7 ± 0.6 mL O₂/kg/min across multiple studies 2
When applying best-practice measurement techniques in older adults, this value drops further to 2.4 ± 0.3 mL O₂/kg/min (approximately 30% lower than the standard value) 2
Direct assessment using indirect calorimetry is recommended for adults ≥60 years rather than assuming the conventional 3.5 mL O₂/kg/min 2
Maximal Oxygen Consumption (VO₂ max)
For context on exercise capacity, maximal oxygen consumption varies significantly by age and sex:
- Men aged 20-29: 43 ± 7.2 mL O₂/kg/min (approximately 12 METs) 1
- Women aged 20-29: 36 ± 6.9 mL O₂/kg/min (approximately 10 METs) 1
- Men aged 60-69: 33 ± 7.3 mL O₂/kg/min (approximately 9 METs) 1
- Women aged 60-69: 27 ± 4.7 mL O₂/kg/min (approximately 8 METs) 1
These maximal values represent the greatest amount of oxygen a person can consume during dynamic exercise involving large muscle groups and are considered the best measure of cardiovascular fitness 1
Clinical Measurement Considerations
Indirect calorimetry remains the gold standard for measuring actual oxygen consumption in clinical settings 2
Metabolic rate meters may underestimate oxygen consumption compared to Douglas bag collection methods, producing values approximately 22% lower than actual measurements 3
Combined heart rate and physical activity monitoring can estimate 24-hour oxygen consumption with mean errors of -3.3 ± 3.5% when properly calibrated 4