Lecture 16

Question 1

best way of measuring energy usage

Answer 1

VO2 and VCO2

Question 2

we are not 100% efficient at converting chemical energy into mechanical energy, how energy is lost as heat

Answer 2

~2/3 of energy lost as heat just to make ATP oxidatively

Question 3

what is calorimetry

Answer 3

the measurement of metabolic energy transformation

Question 4

if you are not doing anything energy will be released as ….

Answer 4

heat

Question 5

if you are doing something energy will be released as …

Answer 5

heat and mechanical energy

Question 6

what is mechanical energy and how can it be measured

Answer 6

work rate

measurable using ergometers or estimations

Question 7

what form of calorimetry is a bomb calorimeter

Answer 7

direct calorimetry

Question 8

how does a bomb calorimeter work

Answer 8

measures energy released from combustion of food

Question 9

who is a bomb calorimeter useful for

Answer 9

useful for nutrition and dietetics

Question 10

what is a bomb calorimeter not useful for

Answer 10

• clinical exercise physioloigy
• sport exercise physiology
• ergonomics

Question 11

what form of calorimetry is whole body calorimeter

Answer 11

direct calorimetry

Question 12

how does whole body calorimeter work

Answer 12

measures body heat production, uses an insulated room

Question 13

who is a whole body calorimeter useful for

Answer 13

useful for nutrition, dietetics, clinical exercise physiology and research

Question 14

what are disadvantages for whole body calorimeter

Answer 14

• expensive
• requires specialist expertise
• restrictive (type of activity and limited time resolution)

Question 15

what type of calorimetry is open circuit spirometry

Answer 15

indirect

Question 16

how does open circuit spirometry work (O2)

Answer 16

indirectly measure rate of energy use by measuring rate of O2 consumed (VO2L.min-1)

Question 17

disadvantages to open circuit spirometry

Answer 17

• doesn’t give instantaneous energy usage
• only useful is steady state
• expensive

Question 18

per L of oxygen which provides more energy, carbs or fat (what is the % difference)

Answer 18

carbohydrates

6% less energy coming from fat than CHO, per L of oxygen

Question 19

if you are unfit or exercising at an intensity too high for you what source of fuel are you most likely to use more of

Answer 19

switch to using more carbohydrates as it provides you more energy faster (glycolysis) also because it gives you more energy per L of oxygen

Question 20

why are you able to use fats as a fuel source for longer if you are fitter

Answer 20

not as O2 limited

Question 21

how does open circuit spirometry work (O2 and CO2)

Answer 21

indirectly measure rate of energy use by measuring rate of O2 consumed and CO2 produced (VCO2L.min-1)

Question 22

what does the ratio of carbon produced per unit oxygen consumed indicate (2)

Answer 22

1. whether some energy is not from aerobic metabolism (R>1.00)
2. relative use of Fat vs CHO being metabolised

Question 23

how do you know the relative use of Fat vs CHO being metabolised

Answer 23

different substrates (food groups) produce different of carbon dioxide when they are oxidised

Question 24

what is the respiratory quotient

Answer 24

RQ = VCO2 / VO2

Question 25

what is the respiratory quotient for carbohydrate metabolism

Answer 25

1.00

for every 6 O2 used, 6 CO2 produced

Question 26

what is the respiratory quotient for fat metabolism

Answer 26

0.70

for every 23 O2 used, 16 CO2 produced

Question 27

what are the three things you must consider when estimating caloric equivalent from RER

Answer 27

• respiratory quotient is at cellular level
• RER reflects RQ only with aerobic metabolism - steady state
• RER > 1.00 reflects loss of CO2 from non oxidative source

Question 28

what is meant by respiratory quotient is at cellular level in terms of estimating caloric equivalent from RER

Answer 28

assume that same as respiratory exchange ratio (RER) measured at the mouth

Question 29

what is the difference between absolute and relative fat and CHO usage (what does it show about fat metabolism adaptation)

Answer 29

you can adapt your fat burning enzymes etc from sprint as well as you can during mutli hour exercise

so this means we don’t know what the best training intensities are for burning fat

Question 30

does HR vs VO2 relationship differ between people

Answer 30

yes

Question 31

what is an issue with predicting VO2 and energy usage from work rate

Answer 31

can be inaccurate, especially with differences in efficiency