Which two values are necessary to calculate the respiratory quotient (RQ)?

The respiratory quotient (RQ) is a valuable measure used in exercise physiology to assess metabolic processes. It is calculated by taking the ratio of the volume of carbon dioxide produced (exhaled) to the volume of oxygen consumed (inhaled) during respiration. This ratio provides insights into which substrates (fats, carbohydrates, or proteins) are being metabolized for energy.

The correct answer focuses on measuring the volume of carbon dioxide exhaled alongside the volume of oxygen inhaled, as this is essential for determining the RQ. Essentially, a high RQ indicates greater reliance on carbohydrates, while a lower RQ suggests more fat utilization.

The other options do not provide the correct combination of measurements needed for RQ calculation. For example, measuring nitrogen or oxygen exhaled does not directly relate to attempting to ascertain how much energy is being derived from different fuel sources. Moreover, focusing on nutrients absorbed does not capture the ratio of carbon dioxide produced to oxygen consumed necessary for RQ calculations. Understanding these elements is essential for applying RQ in practical scenarios, such as tailoring nutrition and exercise programs for clients.