Metabolic rate is a measure of how much food, or fat, is converted to energy in a day. Resting metabolic rate (RMR) is the measurement of how much food, or energy, is required to maintain basic body functions such as heartbeat, breathing, and maintenance of body heat while you are in a state of rest. That energy is expressed in calories per day. So an RMR test shows how many calories you burn at rest, doing nothing more than sitting in a chair.
Indirect calorimetry (a measurement of metabolic rate) relies on the fact that burning 1 calorie (Kilocalorie) requires 208.06 milliliters of oxygen. Because of this very direct relationship between caloric burn and oxygen consumed, measurements of oxygen uptake (VO2) and caloric burn rate are virtually interchangeable.
Oxygen uptake requires a precise measurement of the volume of expired air and of the
concentrations of oxygen in the inspired and expired air. The process requires that all of the air a person breathes out be collected and analyzed while they rest quietly. The KORRTM indirect calorimeters contain a precision air flow sensor that measures the volume of expired air, and an oxygen sensor that measures the concentration of oxygen. Once the factors of humidity, temperature and relative humidity are accounted for, the KORRTM instrument provides the most accurate results available in a compact metabolic analyzer.

Pre-test Requirements
It is desirable to measure a person’s metabolic rate at a true resting level. To ensure one is at rest, we recommend the following preparation:
1. Avoid eating a meal 4 hours before the test.
2. Avoid exercising on the day of testing.
3. If possible, avoid the use of stimulants such as caffeine prior to testing.
4. During the test it will be important to get into a comfortable position and relax as much as possible.
5. Keep lips sealed lightly around the mouthpiece. It is important that all the air breathed out is analyzed by the MetaChe