Kin 310: Lecture 2 - Energy Expenditure

Key terms from Lecture 2: Energy Expenditure, direct and indirect calorimetry, VO2 measurements, open-circuit spirometry, VO2max, METs, and related concepts.

Energy expenditure

The body's use of energy to perform work, measurable directly as heat or indirectly via oxygen consumption (VO2).

Direct calorimetry

Measurement of heat production using a closed chamber (calorimeter) to quantify calories.

Calorimeter

A closed chamber used to measure the amount of heat produced by the body.

Indirect calorimetry

Estimation of energy expenditure from oxygen consumption, using the relationship between O2 use and heat; approx. 5 kcal per L of O2.

VO2

Volume of oxygen consumed per minute; a measure of oxygen uptake and energy production.

VE (ventilation)

Volume of expired air per minute.

FIO2

Fraction of inspired O2 in the air inspired by the person.

FEO2

Fraction of expired O2 in the air exhaled.

VO2 = VE × (FIO2 – FEO2)

Equation used to calculate VO2 from ventilation and O2 fractions.

Open-circuit spirometry

Open-circuit spirometry method using a metabolic cart to measure O2 and CO2 in expired air with a mixing chamber, gas analyzers, and a pneumotach.

Metabolic cart

Computer-based system used in open-circuit spirometry to analyze expired gases.

Mixing chamber

Part of the metabolic cart where expired gas is collected.

Gas analyzers

Devices that measure O2 and CO2 concentrations in expired air.

Pneumotach

Device that measures the volume of air moved during breathing.

Douglas bags

A traditional method of collecting expired air for later analysis.

VO2max

Maximal oxygen consumption achieved during a graded exercise test.

Absolute VO2

VO2 expressed as liters per minute (L/min).

Relative VO2

VO2 expressed as milliliters per kilogram per minute (ml/kg/min).

MET (Metabolic Equivalent of Task)

Unit for expressing exercise intensity; 1 MET = 3.5 ml/kg/min.

kcal/min

Rate of energy expenditure; calories burned per minute (equals VO2 in L/min × 5 kcal per L O2).

kcal (kilocalorie)

Unit of energy; 1 kcal = 1000 calories; commonly used to express energy expenditure.

5 kcal per L O2

Approximate energy yield for each liter of O2 consumed.

ATP

Adenosine triphosphate; the main energy currency of the cell.

Bioenergetics

Study of energy flow and transformation in living systems that enables ATP production.

Resting metabolic rate

Energy expenditure at rest; baseline energy use often estimated via indirect calorimetry.