Learning Module 3:Measuring Metabolic Rate

Clark J Cotton

Measuring Metabolic Rate

Metabolic Rate: the sum of all energetic processes occuring in the body.

Measuring Metabolic Rate

Metabolic Rate: the sum of all energetic processes occuring in the body.

How do you measure metabolic rate?

Measuring Metabolic Rate

Metabolic Rate: the sum of all energetic processes occuring in the body.

How do you measure metabolic rate?– Direct Calorimetry

Measuring Metabolic Rate

Metabolic Rate: the sum of all energetic processes occuring in the body.

How do you measure metabolic rate?– Direct Calorimetry– Mass Balance

Measuring Metabolic Rate

Metabolic Rate: the sum of all energetic processes occuring in the body.

How do you measure metabolic rate?– Direct Calorimetry– Mass Balance– Oxygen Consumption

What’s Oxygen Got to do with It?

• Oxygen is the basic reducing compound used to convert sugar to carbon dioxide, releasing energy for our bodies and producing carbon dioxide.

• Depending on level of activity, almost all of our metabolism is dependent on oxygen.

6 O2 + C6H12O6 6 CO2 + 6 H2O

Measuring Metabolic Rate

• Materials: 1 empty milk jug, plastic tubing, 500ml beaker, permanent markers.

• Gradually fill up milk jug in 500ml increments, mark each addition.

• Flip jug upside down in tub of water and insert plastic tube.

• If you breath in through your nose, and out through your mouth you can calculate the amount of air you breath.

Tidal Volumes

• Tidal volume is the volume of air you inhale and then exhale with each breath.

Vital Capacity

• Vital Capacity is the maximum amount of air that you can inhale and exhale.

Dead Space

• Dead space volume is the volume of air that does not participate in gas exchange because of airway volume. Dead space volume (ml) = body weight (kg) * 2.2

Total Lung Capacity

• Total lung capacity is equal to the vital capacity + the dead space.

Measuring Metabolic Rate

• If you know the number of breaths you take per minute, and the average volume of air per breath, you can calculate the total volume of air you’re breathing per hour.

• Assuming that the air you breath contains 21% oxygen, and the air you exhale contains 17% oxygen, you can calculate your total oxygen consumption per hour.

Example:15 breaths / minute500ml air / breath

450 L air / hour

(.21*450) – (.17*450) = 18 L O2 per hour

Possibilities with Metabolic Rate Measurements

Effects of:• Age• Exercise• Size• Temperature• Time of Day

Possibilities with Metabolic Rate Measurements

Effects of:• Age• Exercise• Size• Temperature• Time of Day

Possibilities with Metabolic Rate Measurements

Effects of:• Age• Exercise• Size• Temperature• Time of Day

Possibilities with Metabolic Rate Measurements

Effects of:• Age• Exercise• Size• Temperature• Time of Day

Possibilities with Metabolic Rate Measurements

Effects of:• Age• Exercise• Size• Temperature• Time of Day