Respiratory Exchange Ratio indicates which of the following?

Respiratory Exchange Ratio indicates which of the following?

• A. Ratio of carbon dioxide released to oxygen consumed
• B. Ratio of lactate to oxygen
• C. Rate of carbon dioxide production
• D. Total energy expenditure

Answer: (A)

The main idea is that the respiratory exchange ratio shows how the body balances oxygen use with carbon dioxide production during metabolism. It is the ratio of carbon dioxide released (VCO2) to oxygen consumed (VO2). This tells you which fuels are being burned: values around 0.7 indicate fat oxidation, around 1.0 indicate carbohydrate oxidation, and intermediate values reflect a mix. During intense exercise, RER can exceed 1.0 due to factors like buffering of lactate that increase CO2 from non-metabolic sources. The other options don’t fit because RER isn’t a lactate-to-oxygen ratio, nor is it simply the rate of CO2 production, and it doesn’t by itself measure total energy expenditure (that requires VO2 and the RER to estimate calories).

The main idea is that the respiratory exchange ratio shows how the body balances oxygen use with carbon dioxide production during metabolism. It is the ratio of carbon dioxide released (VCO2) to oxygen consumed (VO2). This tells you which fuels are being burned: values around 0.7 indicate fat oxidation, around 1.0 indicate carbohydrate oxidation, and intermediate values reflect a mix. During intense exercise, RER can exceed 1.0 due to factors like buffering of lactate that increase CO2 from non-metabolic sources. The other options don’t fit because RER isn’t a lactate-to-oxygen ratio, nor is it simply the rate of CO2 production, and it doesn’t by itself measure total energy expenditure (that requires VO2 and the RER to estimate calories).