Lecture 19

Question 1

When we are exercising, we are activating __________ muscles. This means that we need activate _________ systems to make energy, and for that he needs to get oxygen to the skeletal muscles, so the ____________ and _____________ systems have to kick in.

Answer 1

Skeletal
energy
cardiovascular
respiratory

Question 2

What three things occur when we are exercising?

Answer 2

• muscles are contracting
• there is increased respiratory rate
• heart rate and contraction increases

Question 3

What does muscle composition refer to?

Answer 3

the ratio of muscle fibre types

Question 4

Describe the two types of muscle fibres

Answer 4

Type II (a and x)/ fast twitch: peak tension in 50ms

Type I/slow twitch: peak tension in 110 ms

Question 5

What can the type II fibres be divided into? Describe these

Answer 5

Type II a (intermediate fibres) and type II x fibres (really fast explosive fibres)

Question 6

Why are we interested in measuring the muscle fibre types in muscles of athletes?

Answer 6

Because muscle fibres have really large differences in their contractile speeds

Question 7

Describe the power of the muscle types

Answer 7

Fast twitch fibres produce a lot lot power

Question 8

Describe the fatigue of the muscle types

Answer 8

Type I has a lot more resistance to fatigue

Question 9

Describe type 2 a fibres?

Answer 9

They are in the middle of fast and slow twitch and can be pushed in either direction. They have both metabolic and mechanical potential where they can become very very oxidative like Type 1 or be made to produce a lot of power like type 2 x

Question 10

What determines what type of muscle fibres you have?

Answer 10

• 50% genetic link
• early life sports can influence adult levels of muscle types (in younger individuals there is a given proportion of hybrid fibres that share some of the characteristics of either one of these fibres, and those hybrid fibres can specialize and become either type 1 or type 2 depending on what you do at a very young age)

There can also be shifts in the fibre type composition but really only in those type 2 subtypes. Type IIx fibres for example if you went and did a whole lot of endurance training then after a few weeks they would shift into the type II a intermediate fibres. What doesn’t seem to happen in the short and moderate term, a type 1 will not shift into a type 2 fibre. So really in the short to moderate term, only shifts within the type 2 fibres.

Question 11

What is magnetic resonance spectroscopy?

Answer 11

MRI technicians will scan different muscles in athletes measuring a particular metabolite in skeletal muscle called carnosine.

Question 12

What is carnosine?

Answer 12

This is 2 times higher in your muscle fast twitch fibres than your slow twitch fibres. Carnosine is very stable in muscles in response to training, and is not very responsive to diet changes. However, one supplement that does affect is beta alanine.
Carnosine buffers H+ ions. Because more H+ is produced in type II fibres, we can estimate what type of muscle fibres you have

Question 13

Describe the type 1 fibres during exercise

Answer 13

There is high aerobic endurance. This means that we can maintain exercise for prolonged periods and it requires oxygen for ATP production.
It efficiently produces ATP from fat and carbohydrate

Question 14

Describe type II fibres during exercise

Answer 14

Poor aerobic endurance, fatigues quickly
- Type IIx (fast) is seldom used for everyday activities and is instead used for explosive sprints
- Type II a (intermediate)
there is more force, faster fatigue than type I for short, high-intensity endurance events

Question 15

Summary of muscle fibre types are found on what slide?

Answer 15

15

Question 16

As intensity increases, the recruitment order of muscle fibre types is

Answer 16

Type I, Type IIa, Type IIx

Question 17

What is the energy for metabolism?

Answer 17

ATP

Question 18

Where do we get ATP from?

Answer 18

We have very limited ATP stores because what we do have is converted to ADP and Pi by ATPase. We must constantly synthesise new fuel stores

Question 19

What is the fast ATP generation pathway?

Answer 19

the phosphocreatine pathway

Question 20

Describe the phosphocreatine (PCr) pathway to generate ATP

Answer 20

This is a fast ATP generation. When ATP is used by ATPase, the ADP and Pi can be recycled to make more ATP from PCr. PCr is broken down into creatine and Pi and free energy and then the Pi and ADP are combined to form ATP. PCr can recycle ATP during exercise until it is used up. It is anaerobic.

Question 21

How many ATP are yielded from one PCr?

Answer 21

1

Question 22

After how long are the PCr stores used up?

Answer 22

3-15 seconds

Question 23

Describe the glycolysis pathway to generate ATP

Answer 23

This is a fast ATP generation. There is no O2 required. Glucose is converted to pyruvate via a series of steps which produces 2 ATP.

Question 24

What is the energy substrate in the glycolysis pathway?

Answer 24

muscle glycogen stores

Question 25

The amount of glucose stored in the muscle allows us to use the glycolysis pathway for how long until the stores are used up?

Answer 25

15s - 2 mins

Question 26

What are the two slow ATP generation pathways?

Answer 26

the TCA pathway

oxidation of fat (lipids)

Question 27

Describe the TCA pathway for generating ATP

Answer 27

Oxygen is required. Pyruvate is converted to acetyl-CoA and through many steps, CO2 is produced as waste, cofactors are produces and GTP. In the process, 32-34 ATP are made.

Question 28

Describe the oxidation of lipids

Answer 28

Fat stores are converted into fatty acids and glycerol. Fatty acids can enter β oxidation and the glycerol is converted to acetyl-CoA to enter the CAC. Overall there is a total of 460 ATP produced

Question 29

How can protein act as a fuel source?

Answer 29

This is normally due to starvation. Protein is converted to amino acids and then to glucose then to acetyl-CoA to enter the citric acid cycle

Question 30

What is ATP needed for?

Answer 30

for contraction/relaxation

Question 31

What slide is a good summary slide?

Answer 31

slide 26

Question 32

Which muscle fibre type are termed fatigue resistant?

a. Fast twitch (Type IIx)
b. Intermediate twitch (Type IIa)
c. Slow twitch(Type I)
d. None of the above

Answer 32

c. Slow twitch(Type I)

Question 33

Phosphocreatine (PCr):

a. is a substitute for troponin in smooth muscle
b. destroys excess acetylcholine (ACh) at the neuromuscular junction
c. stores energy from ATP in the muscle cell
d. is a neurotransmitter found in smooth muscle

Answer 33

c. stores energy from ATP in the muscle cell

Question 34

A muscle fibre gains 60 ATP’s from metabolism. How many glucose molecules were consumed to yield this much energy if the muscle fibre is operating anaerobically?

a. 120
b. 30
c. 38
d. 2

Answer 34

30

Question 35

Weightlifters training anaerobically (for strength rather than endurance) emphasize which muscle type?

a. Slow twitch (Type I)
b. Fast twitch (Type Iix)
c. Neither
d. Both

Answer 35

b. Fast twitch (Type Iix)