PEMES 3153 Physiology of Exercise
Maximal Oxygen Consumption
Before coming to lab review the section entitled “Measuring Energy Expenditure” on pages 114-116 in
your text. Read the article on the website entitled “Criteria for VO2max” located directly after this lab
on the webpage. Understand the criteria for determining if VO2max had been achieved.
Introduction
Heat is produced as a result of cellular respiration and cellular work. An operational definition of metabolism is
the rate of heat production which describes the metabolic rate.
The direct measure of heat production, called direct calorimetry, is a technically difficult procedure. An
alternative method measures the volume of oxygen consumed by the body for ATP production. The
determination of the metabolic rate from the measure of oxygen consumption is called indirect calorimetry.
In our laboratory, we utilize a metabolic measurement cart for
indirect calorimetry measurements. This system measures the
total volume of ventilated air as well as the differences of
oxygen and carbon dioxide levels from the ambient and expired
air. The system’s computer uses this information to calculate the
volume of oxygen utilization (VO2) and carbon dioxide
production (VCO2).
To yield these measurements, a subject is fitted with a lowresistant, two-way non-rebreathing valve in her/his mouth which
directs all expired air to the metabolic measurement cart via a
long flexible hose. As the expiratory air enters the cart, it passes
through an instrument which measures air volume. The air
enters a mixing chamber from which a small sampling line
draws air from the mixing chamber to an O2 and CO2 analyzer
which are interfaced, along with the air-flow meter, to a
computer making the necessary computations.
subject
expired air
volume analyzer
O2 analyzer
mixing
chamber
CO2 analyzer
computer
The measurement of maximal oxygen consumption (VO2max) has long been used to evaluate aerobic fitness.
In performance, this measure is strongly related to endurance activities of short duration (one mile run) and
moderately related to longer endurance (10K run and longer) tasks. In health, this measure has been linked to
cardiorespiratory function as well as skeletal muscle oxygen consumption capabilities. Thus it has been viewed
as the measure that reflects cardiorespiratory endurance, one of the health-related fitness components.
Assessing a direct measure of VO2max requires laboratory instrumentation (metabolic cart), a mode of exercise
that utilizes a lot of muscle (ex - running, biking), an appropriate test protocol that minimizes oxygen deficit,
and a motivated subject to perform a continuous test until exhaustion. While this is possible in an Exercise
Physiology Laboratory, it is less practical in most wellness centers, sports medicine rehabilitative centers, and
schools. Therefore many times tests are used to indirectly evaluate VO2max based upon performance to
maximal efforts (time to fatigue on a progressive treadmill test), time in an aerobic task (1.5 mile test), or using
the submaximal response to exercise and estimating the VO2max (heart rate response during a walking test).
The purpose of this laboratory is to demonstrate a VO2max test using indirect calorimetry and learn the criteria
for assessing whether a true VO2max value was obtained. Differences in VO2max between males and females
will also be evaluated.
Measurement
1. Two volunteer subjects, one male and one female will be solicited. Each will be subjected to a protocol
using the treadmill and metabolic cart to measure the highest rate of oxygen consumption (VO2). A Polar
heart rate transmitter will be used to monitor heart rate during the test.
2. For this laboratory experience, a protocol that starts with a warm-up of 3.5 mph for two minutes, 5.5 mph
for two minutes, and increases the speed 0.5 mph every one minute until a running velocity comfortable for
the subject is reached. Then the grade will be increased 1% every minute until reaching volitional
exhaustion. It is important in this type of maximal effort to provide verbal encouragement for the subject to
motivate him/her during the latter stages of the test.
3. The following variables will be determined each minute of the test: VO2 in ml.kg-1.min-1, VO2 in ml.min-1,
VE in L.min-1, RER, and heart rate.
Analyses
1. Using the article provided, determine if each subject reached a true VO2max and identify the criteria you
used to make that decision.
2. Normally you expect the average male to have a higher VO2max than the average female of the same age
and training level. What are three reasons the average male has a higher VO2max than the average female?
3. If all you knew was the data collected on each subject and that the subjects were equally trained in running
and cycling and were the same age, which subject would do better in a 5 mile running race on a track?
Which would do better on a 10 mile bicycle race over flat terrain? Explain your answers using
physiological principles and rationale.