Direct calorimetry requires the subject to remain inside an enclosed chamber.

• A. True
• B. False
• C. It measures only CO2
• D. It measures only O2

Answer: (A)

Direct calorimetry quantifies energy expenditure by measuring the heat the body produces. To capture all of that heat, the person is placed in an insulated, enclosed chamber. If heat escaped, the calculation would miss part of the energy output, so containment is essential. The other approach estimates energy use from oxygen consumption and carbon dioxide production rather than heat, so it does not require a heat chamber. That’s why this statement is true: direct calorimetry relies on the enclosed chamber to measure total heat production.