Measurements Of Energy Expenditure Flashcards
What are the measurements of energy expenditure?
Indirect calorimetry
Lactate sampling
VO2 max test
Respiratory exchange ratio (RER)
What does indirect calorimetry do?
A technique that provides an accurate estimate of energy expenditure through gas exchange.
It measures how much carbon dioxide is produced and how much oxygen is consumed at both rest and during aerobic exercise.
Calculating the gas volumes also enables us to find out the main substrate being used (fat or carb).
How accurate is indirect calorimetry?
It is very reliable as it gives a precise calculation of VO2 and VO2 max.
What is indirect calorimetry?
Measures the production of CO2 and/or the consumption of O2.
What is lactate sampling?
An accurate and objective measure of the level of blood lactate in the blood.
What does lactate sampling involve?
Taking a tiny blood sample and a handheld device analyses the blood and indicates how much lactate is present.
Who tends to use lactate sampling?
Elite performers in sports such as running, swimming and rowing to monitor training and predict performance.
How else can lactate sampling be used?
As a means of measuring exercise intensity - the higher the exercise intensity at which the lactate threshold occurs, the fitter the athlete is considered to be.
Give an idea of level of fitness
Enable the performer to select relevant training zones.
What can regular lactate sampling do?
Provides a comparison from which the coach and performer can see whether improvement has occurred.
If test results show a lower lactate level at the same intensity of exercise, this should indicate that the performer has an increase in peak speed/power, increased time to exhaustion, improved recovery HR and a high lactate threshold.
What is the respiratory exchange ratio?
The ration of CO2 produced compared to oxygen consumed.
What is the RER used for?
As a measure of exercise intensity.
What does the RER provide?
Information about fuel usage during exercise.
Energy sources such as carbohydrates, fat and protein can all be oxidised to produce energy.
For a certain volume of oxygen, the energy released will depend upon the energy source.
Calculating the RER will determine which of these energy sources is being oxidised and hence whether the performer is working aerobically or anaerobically.
What is the equation of RER?
RER = CO2 expired per min (VCO2) / O2 consumed per min (VO2)
What do the results of RER mean?
A RER value close to 1 = performer using carbs
A RER value of approx 0.7 = performer using fats
A RER value greater than 1 = anaerobic respiration so more CO2 being produced than O2 consumed.
What is the VO2 max test?
The most common test for evaluating VO2 max is the multi-stage fitness test, more commonly known as the ‘bleep’ test.
Here the individual performs a 20m progressive shuttle run to a bleep, until they reach complete exhaustion.
The level that is reached can be compared with a standard results table.
Other tests include the Harvard step test and the Cooper 12-min run, but all of these only give an indication or prediction of VO2 max.
A sport science laboratory can produce much more valid and reliable results using direct gas analysis.
Test using this method involve increasing intensities on a treadmill, cycle ergometer or rowing machine
