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HL22015 physiology > Limits to exercise tolerance 2 > Flashcards

Limits to exercise tolerance 2 Flashcards

1
Q

Arguments against lungs being a limiting factor in VO2max?

A

Alveolar area is v large, ventilation increases more than oxygen uptake, pp of oxygen in alveoli and arteries is maintained at VO2max

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2
Q

Arguments in favour of lungs being a limiting factor in VO2max?

A

At normoxia, the oxygen saturation of haemoglobin declines as the intensity of exercise does, hypoventilation, mechanical constraints

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3
Q

What is hyperoxia?

A

Atmospheric oxygen partial pressure is higher than usual

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4
Q

What is normoxia?

A

Atmospheric oxygen partial pressure is the same as usual

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5
Q

What is hypoxia?

A

Atmospheric oxygen partial pressure is lower than usual

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6
Q

What is hypoventilation?

A

breathing that is too shallow

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7
Q

How can hypoventilation be a limitation of VO2max?

A

Someone may have the capacity for a certain oxygen uptake but arent sensitive enough to the stimuli (exercise) to increase the ventilation rate

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8
Q

What are the axis of a flow volume loop?

A

Flow rate in L/s on Y axis, volume in L on the x axis

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9
Q

How to create a flow volume loop?

A

Maximal inspiration then forcefully expire all air in lungs as quickly and as hard as possible

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10
Q

How can we test whether lung function is a limiting factor of VO2?

A

Changing density of inspired air

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11
Q

What was observed as a result of changing the density of inspired air to see whether?

A

Less dense air overcomes the limitation of lungs reaching expiring capacity

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12
Q

What is pulmonary oedema?

A

Swelling in the lungs

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13
Q

How does pulmonary oedema negatively affect gas exchange in the lungs?

A

The swelling causes the interstitial space between the alveoli and capillary to increase thus gas exchange takes longer

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14
Q

How can alveolar capillary diffusion limit VO2max?

A

Only one RBC can pass through a capillary at a time. In untrained this is 0.4-0.5s whereas in trained it is <0.4. Longer means more time to take oxygen to blood so lower VO2max

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15
Q

Are lungs a limiting VO2max factor in untrained individuals?

A

Not a huge amount of evidence to support it

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16
Q

Are lungs a limiting VO2max factor in trained individuals?

A

Some evidence that this may be true

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17
Q

What is hyperpnea?

A

Increased ventilation

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18
Q

What is the cost of exercise hyperpnea?

A

Respiratory muscles have a power output of around 50 watts

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19
Q

WHat is unique about respiratory muscles?

A

They can produce a lot of force relative to their size

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20
Q

What is proportional assisted ventlation?

A

Participant begins inhaling–> rest of air is forced into lungs via machine

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21
Q

What is RPE?

A

Rating of perceived exertion

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22
Q

What happens to leg RPE in unloaded (proportional assisted ventilation) condition?

A

It is a lot lower than load or control

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23
Q

How to load inhalation?

A

Have the participant lift a small weight when they breathe in–> lungs and respiratory muscles have to work harder

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24
Q

What is an MIP?

A

Maximum inspiratory mouth pressure test

25
Q

What does a MIP do?

A

Measures the pressure someone can generate at their mouth when they breathe in

26
Q

What happens to MIP following exercise?

A

It decreases

27
Q

Issue with doing an MIP after endurance exercise?

A

Athletes may be tired and so might not inspire as hard as they can

28
Q

What is a volitional measure?

A

Relating to someones will

29
Q

How is the diaphragm isolated when measuring its exertion?

A

Using a nasoesophageal catheter

30
Q

How does a nasoesophageal catheter work work?

A

It goes up the nose, down the throat and into the stomach where there is two pressure transducers, one in the stomach and one in the oesophagus. WHen diaphragm contracts it moves down which increases stomach pressure and decreases esophageal pressure

31
Q

What is the respiratory metaboreflex?

A

When respiratory muscles become fatigued, it sends a signal that changes blood flow to other muscles

32
Q

What is observed regarding leg blood flow when work of breathing is increased?

A

It decreases

33
Q

When using a nasoesophageal catheter, where are the pressure transducers?

A

Stomach and oesophagus

34
Q

What is observed regarding leg VO2 when work of breathing is increased?

A

It decreases

35
Q

How efficient is muscle O2 extraction?

A

Very

36
Q

Why is muscle oxygen extraction unlikely to limit VO2max?

A

At high intensity exercise the difference in oxygen conc between the artery entering the muscle and the vein leaving the muscle is high meaning it is very efficient

37
Q

What explains most of the variance in VO2max between people?

A

Cardiac output

38
Q

What explains the early increase in VO2max with exercise training?

A

Plasma volume

39
Q

What is observed in the blood in the first week after beginning training?

A

Rapid increase in plasma volume

40
Q

How to artificially increase plasma volume?

A

Dextran infusion

41
Q

What is observed in the VO2max of people who have had their blood plasma volume artificially increased as a result of a dextran infusion?

A

An increase of ~4%

42
Q

How does dehydration affect performance?

A

It leads to a lower plasma volume which leads to lower blood flow and stroke volume

43
Q

In most people, what is the correlation between VO2max and performance time in a a marathon?

A

High

44
Q

In elite athletes, what is the correlation between VO2max and performance?

A

Not as strong as in the general population

45
Q

Why may the VO2max of elite athletes not perfectly correlate to performance?

A

other factors such as mechanical efficiency, running economy etc

46
Q

Which test could be better than VO2max for elite athetes?

A

Lactate threshold

47
Q

What was observed regarding time to fatigue differences at 70%VO2max in low, mixed and high CHO diets?

A

The low CHO diet performed the worst with around 1 hr, the high performed the best between 2 and 5 hrs

48
Q

Correlation between CHO content in diet and muscle glycogen levels?

A

Higher CHO content in diet means a higher muscle glycogen content

49
Q

What was observed when looking at the time when muscle glycogen depletion occurs in placebo and CHO-fed groups during exercise?

A

They reach muscle glycogen depletion at the same time (3hrs)

50
Q

Why could CHO-fed people exercise for longer than placebo despite reaching muscle glycogen depletion at the same time?

A

Taking on more CHO means it no longer becomes a reason for fatigue

51
Q

What role can muscle glycogen have other than a fuel?

A

A signalling molecule

52
Q

Subsarcolemmal region meaning?

A

Below the sarcolema

53
Q

Which type of muscle glycogen storage is most closely associated with fatigue?

A

Intramyofibrillar

54
Q

How does a lack of muscle glycogen affect calcium?

A

It affects its release rate

55
Q

Which out of glycogen, glucose, FAs can generate ATP the fastest?

A

Glycogen

56
Q

What is McArdles disease?

A

Lack of enzymes required to break down muscle glycogen

57
Q

Which fuel is more efficient, carbs or fats?

A

Carbs

58
Q
A

HL22015 physiology (17 decks)

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