Exercise Physiology: Muscle, Fuels and Fatigue

Question 1

What fuels do type I muscle fibres rely heavily on?

Answer 1

Oxidative fuels, including lipids

Question 2

What is the association between type I fibres and lipid storage?

Answer 2

If you have more type I fibres, you store less lipid

Question 3

What proportion of body mass is made of muscle in most people?

Answer 3

40%

Question 4

Which muscle fibre types are mainly found in humans?

Answer 4

Type I and IIa

Question 5

Which muscle fibre types are probably found only in super sprinters, who are most likely born with them?

Answer 5

Type IIx

Question 6

What is another name for type I fibres?

Answer 6

Slow twitch fibres

Question 7

What is another name for type IIa fibres?

Answer 7

Fast twitch fibres

Question 8

Which muscle fibre type reaches peak tension first?

Answer 8

Type IIa

Question 9

Rank the muscle fibre types in order of force/power output, from highest to lowest

Answer 9

Type IIx >IIa >I

Question 10

Rank the muscle fibre types in order of endurance capacity, from highest to lowest

Answer 10

Type I >IIa >IIx

Question 11

Rank the muscle fibre types in order of proportion in whole muscle, from highest to lowest

Answer 11

Type I >IIa >IIx

Question 12

Rank the muscle fibre types in order of mitochondrial density, from highest to lowest?

Answer 12

Type I >IIa >IIx

Question 13

How do type I fibres in females differ from those in males, and why?

Answer 13

Females have slightly more type I fibres and have more efficient oxidation
Thought to be because of oestrogen

Question 14

As the muscular force generated increases, in which order are muscle fibre types recruited?

Answer 14

Recruit slow twitch, smaller fibres first

Fast twitch fibres recruited next

Question 15

Can muscle fibre types be changed?

Answer 15

Can turn some fast twitch fibres, especially type IIa, into slow twitch fibres
No real evidence to show switch from slow twitch fibres to fast twitch

Question 16

In response to high-intensity resistance training, what is the rate of neural and muscle adaptations?

Answer 16

Neural adaptations happen very quickly, but muscle adaptation much slower

Question 17

What is the relationship between muscle mass and disuse?

Answer 17

Muscle mass lost very quickly with inactivity

Question 18

What does bed rest activate in muscles?

Answer 18

Atrophy proteins via unknown mechanism

Question 19

What are the mitchochondrial adaptations to exercise training?

Answer 19

Increased mitochondrial density and oxidative enzymes
Reduced carbohydrate use and lactate production
Increased fat oxidation
Enhanced endurance performance
Improved insulin action

Question 20

What is the relationship between exercise and skeletal muscle GLUT4 expression?

Answer 20

Exercise activates GLUT4 expression in muscles, independent of insulin

Question 21

How long do ATP stores in muscle last for during exercise?

Answer 21

2-15 sec

Question 22

What can creatine phosphate do during explosive activity?

Answer 22

Transfer its phosphate to ADP

Question 23

What happens to the rate of exercise when using lipids as an energy source, and why?

Answer 23

Becomes slower

Rate of ATP production significantly slower when using free fatty acids compared to carbohydrates

Question 24

Is the amount of ATP that can be generated from free fatty acid oxidation limited?

Answer 24

No, not even in very skinny marathon runner

Question 25

What is the relative use of fuels during different duration sprints?

Answer 25

Power output decreases with increasing duration Amount of glycolysis doesn't really change Energy from phosphocreatine makes significant contribution, which decreases with time

Question 26

What is the relative use of fuels during different intensities of exercise?

Answer 26

As exercise intensity increases, glycogen becomes most important fuel source Fat usage increases with intensity, then decreases, until it will eventually stop

Question 27

What are some factors influencing exercise metabolism?

Answer 27

``` Exercise intensity and duration Diet Training Environmental temperature Age and gender ```

Question 28

How does training influence fat utilisation?

Answer 28

With training, increase fat utilisation for given exercise intensity

Question 29

How does the environmental temperature influence fuel usage during exercise?

Answer 29

Increased temperature > increased carbohydrate use

Question 30

What is fatigue?

Answer 30

Reduction in force and power generating capacity

Question 31

What is fatigue induced by?

Answer 31

Muscle contractile activity

Question 32

Is fatigue reversible?

Answer 32

Yes

Question 33

What is weakness induced by?

Answer 33

Happens at rest, and would probably be exacerbated by muscle contractile activity

Question 34

As you undertake a required force, your maximum possible force decreases. When does this become a problem?

Answer 34

Maximum possible force becomes less than required force

Question 35

What happens when muscle glycogen stores are depleted during exercise?

Answer 35

Unable to maintain exercise intensity

Question 36

What effect does carbohydrate ingestion before exercise have on your exercise capacity?

Answer 36

Improves it