Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Chapter 8
Measurement of Human Energy Expenditure
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Methods of Measuring Body’sHeat Production
Two methods
• Direct calorimetry
• Indirect calorimetry
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Direct Calorimetry
• Airflow calorimeter– Temperature change in air that flows through
an insulated space × air’s mass and specific heat
• Water flow calorimeter– Change in temperature flowing through coils
embedded in an environmentally self-contained suit
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Direct Calorimetry
• Gradient layer calorimetry– Measures heat flowing from the subject through
a sheet of insulating materials with piping and cooler water on outside
• Storage calorimetry– Subject sits in a known mass of water at a
constant temperature. Changes in water temperature are measured.
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Indirect Calorimetry
• Closed-circuit spirometry– Subject breathes into a spirometer.– Soda lime is used to absorb carbon dioxide.
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Indirect Calorimetry
• Open-circuit spirometry– Portable spirometry
• Spirometer is small and is carried in a pack.
• Air volume is metered.
• Sample is collected to measure concentrations of gases.
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Indirect Calorimetry
• Bag technique– Air is collected in a large bag (Douglas Bag).– Small sample is measured for gas
concentrations.
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Indirect Calorimetry
• Computerized instrumentation– Air flow is measured for volume.– Gas analyzers measure concentrations of oxygen
and carbon dioxide.
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Doubly Labeled Water Technique• Isotope-based method
• Doubly labeled water contains– Oxygen-18 or 18O– Deuterium or 2H
• Isotopes consumed in a known volume of water
• Isotopes distribute throughout body fluids
• Hydrogen leaves body as 2H2O in sweat and urine
• Oxygen leaves body as C18O2 or H218O
• Estimates total daily energy expenditure
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
The Respiratory Quotient (RQ)• RQ = CO2 produced / O2 consumed
– RQ for carbohydrate = 1.00– RQ for fat = 0.696– RQ for protein = 0.818– Nonprotein RQ = 0.86– RQ for a mixed diet = 0.82
• RQ – assume that oxygen consumption and carbon dioxide production measured at mouth reflect activity in tissues
Copyright © 2007 Lippincott Williams & Wilkins. McArdle, Katch, and Katch: Exercise Physiology: Energy, Nutrition, and Human Performance, Sixth Edition
Respiratory Exchange Ratio (RER)
• Ratio of CO2 produced to O2 consumed
• Calculation of RER is the same as RQ
• Metabolic calculations– Calculating energy expenditure during exercise– Volume of air
– Concentrations of O2 and CO2