Measurement of oxygen intake by a person about 14 hours after eating as an indication of the amount of energy required to maintain vital body functions (e.g., circulation, respiration, digestion). Breathing into a tube that leads to a measuring apparatus, the person remains at rest (but does not sleep) during the test. For each interval of time, the more oxygen consumed, the more oxidation is occurring and the higher is the basal metabolic rate (BMR). The test has largely been replaced by newer techniques.