GLOSSARY

Oxygen Consumption describes oxygen use within a specified whole-body, cellular or process boundary.

Respiratory quotient relates metabolic carbon dioxide production to oxygen use; respiratory exchange ratio measures the corresponding external gas exchange. They can approximate each other at steady state, but ventilation and buffering during hard exercise separate them. A high value is not automatically an exact carbohydrate percentage. Nonprotein calculations correct protein contribution under defined assumptions. Identify measurement level and conditions rather than treating every breathing ratio as a precise intracellular fuel measurement in all situations.

Direct calorimetry measures heat; indirect approaches estimate energy through gas exchange. Metabolic carts need calibration, sound collection and appropriate stable conditions. Substrate calculations have assumptions and do not interpret every intensity or rapid transition equally well. Record feeding, activity and test purpose. A device value is not error-free reality or an independent diet prescription, and comparing measurements requires method consistency rather than merely matching the equipment's displayed units.

Mitochondrial respiration passes carrier electrons through a chain to oxygen as final acceptor, forming water and supporting a gradient. Oxygen use and ATP output are related without an immutable ratio. Whole-body oxygen consumption is not exclusively working-muscle metabolism. Distinguish cellular, tissue and respiratory measurements. A higher oxygen-use value can reflect greater demand rather than automatically greater efficiency, and the test context determines what capacity or function can be inferred.