The RQ is determined by the use of a metabolic cart. Individuals breathe into a mask for 3-5 minutes after a rest period of 30 or more minutes. The ratio of exhaled volume of CO2 to the inhaled volume of O2 is determined as the RQ. The physiologic range is 0.7 to1.3. Individuals using fat as a primary fuel have a ratio of 0.7, protein or mixed fuels is 0.8-0.9 and carbohydrate is 0.9-1.0. Those taking excessive calories will have RQ's higher than 1.05.