Energy systems and balance

Question 1

What are the 3 categories of biological work?

Answer 1

1. Mechanical (e.g. muscle contraction)
2. Chemical (e.g. glucose – glycogen)
3. Transport (e.g. active transport)

Question 2

How de we re-synthesize ATP in the immediate, short and long term?

Answer 2

immediate: ATP-PCr system
short term: glycolytic system
long-term: oxidative system

Question 3

Roughly how much energy is lost during ATP synthesis as heat?

Answer 3

60-70%

Question 4

Describe the two methods of studying metabolism

Answer 4

Direct calorimetry: measures heat

Indirect calorimetry: measures O2 intake and CO2 production

Question 5

What is the formula for respiratory exchange ratio (RER)?

Answer 5

VCO2/VO2

Question 6

What use is RER and what are the standard values you may observe?

Answer 6

RER gives an indication of substrate mix
usually between 0.7 and 1
RER > 1 when one is hyperventilating or undergoing intense exercise

Question 7

What happens to substrate utilisation as exercise intensity increases?

Answer 7

More CHO utilised than fat.
The crossover point occurs at about 50% of VO2 max.
- (Venables et al, 2005)

Muscle glycogen provides majority of energy above 65% VO2 max, taking over from plasma FFA.
- (Romjin et al, 1993)

Question 8

Energy balance = ?

Answer 8

energy intake - total energy expenditure

Question 9

What makes up energy expenditure?

Answer 9

> physical activity (15-45%)
DIT (10%)
BMR/RMR (50-75%)

Question 10

What explains the majority of variance in BMR within humans?

Answer 10

fat free mass (~63%)

- (Johnstone et al, 2005)

Question 11

Physical activity level (PAL)?

Answer 11

total energy expenditure / BMR

Question 12

How does direct calorimetry measure energy expenditure?

Answer 12

measures heat loss from participant

Question 13

What are some issues associated with direct calorimetry?

Answer 13

X can’t monitor rapid changes
X can’t determine fuel use
X space limitations
X exercise equipment = friction = heat

Question 14

How do indirect calorimetry methods measure energy expenditure?

Answer 14

measuring O2 consumption and CO2 production

Question 15

What are some issues associated with indirect calorimetry?

Answer 15

X measuring affecting behaviour
X difficulty in long term use
X difficult outside of lab

Question 16

How could you perform indirect calorimetry over a period of days?

Answer 16

> Doubly labeled water

> self report / recall

Question 17

How does doubly labelled water work?

Answer 17

Uses heavy stable isotopes 2H and 18O.
H lost as H2O, but O lost as H2O AND CO2.
The difference in rates of elimination is used to estimate CO2 production.

Question 18

Critique doubly labelled water

Answer 18

X expensive
X expertise and equipment required
X no info about substrate use
X no short term use (7-14 days)

Question 19

How are self-report and recall measures utilised for the purposes of indirect calorimetry?

Answer 19

activity diaries utilising ~15 minute periods throughout the day to register and activity or MET score

Question 20

What are some issues with using self-report and recall measures?

Answer 20

X recall issues
X time-consuming for ppt and experimenter
X not sensitive

Question 21

Give some examples of non calorimetric methods of assessing energy expenditure and their pros/cons

Answer 21

> Pedometer + accelerometers:
$ cheap and accessible
$ good for ambulatory activity
X misses static activity (e.g. lifting or cycling)

> HR monitors
$ accessible
$ based on fairly linear relationship between HR and EE
X HR affected by other factors (e.g. stress)
X Poorer at lower intensities
X HR is highly variable between people

> Multi-sensort devices
$ multiple sensors reduces the error influence of a singular device

Question 22

What is an issue associated with physical activity wearables?

Answer 22

Can vary greatly between activities.

The error of different bands varies, therefore can’t compare between them.
- (Chowdhury et al, 2017)

Question 23

How would you establish the total energy of food?

Answer 23

combustion

Question 24

What are 3 methods of assessing energy intake?

> What are some issues with these methods?

Answer 24

1. food diaries
2. food recall questionnaire
3. weighing food + fluid intake

> 1, 2 and 3 are time-consuming in the process and analysis.
1, 2 and 3 also may lead to Hawthorne effect (altering behaviours due to being observed)
1 and 2 are open to recall errors

Question 25

What’s the upper limit for acute energy expenditure?

Answer 25

~23XRMR when running 4 minute miles.
for very short periods of time, very high energy expenditures can be achieved
- (Ainsworth et al, 2011)

Question 26

In the short term, can energy intake or expenditure be higher?

Answer 26

acute energy intake > energy expenditure

Question 27

In the long term, can energy intake or expenditure be higher?

Answer 27

long term energy intake < energy expenditure

Question 28

Are changes in body mass over time linear?

Answer 28

Rarely…
reducing energy intake by 500 kcal a day wouldn’t lead to 0.5 kg loss every week because as mass reduces, RMR and PAEE also decrease.