L288 Exercise Physiology - Muscles, Fuels and Fatigue

Question 1

What kind of muscle fibre is correlated with lower body fat % and why?

Answer 1

• ↑ % Type I fibres, ↓ body fat % - because type I fibres have greater oxidative capacity than type II

Question 2

Human muscle fibre types: how do they stain with different pH solutions?

Answer 2

• Type 1 fibres stain dark after acidic, and type II dark after alkaline, pre-incubation

Question 3

List the different muscle fibre types

Answer 3

1. Type I (slow-twitch)

2. Type II (fast-twitch): IIa and IIx

Question 4

Characteristics of type I fibres

Answer 4

• oxidative , high mitochondrial density
• MHCI, well vascularised
• Low and slow force generation, fatigue-resistant

Question 5

Type IIa vs IIx fibre characteristics

Answer 5

IIa:

• MHCII
• medium vascularity, mit density, vascularity, force gen and time to force gen
• fatigue-resistant

IIx:

• MHCII
• low vascularity, mit density, vascularity, force gen and time to force gen
• fatigue susceptible

Question 6

Type IIx fibres: in whom are they usually found and why?

Answer 6

Sprinters - hard to train muscles to increase IIx fibres - pretty much born with it

Question 7

Muscle fibre type: order of recruitment

Answer 7

I fibres first, then IIa, then IIx last

Question 8

Fibre type recruitment depends on which two factors?

Answer 8

A. Intensity

B. Duration (of exercise)

Question 9

Muscle fibre phenotype: what is it dependent on?

Answer 9

A. genetics

B. training: to fully express the phenotype you’re born with, you need to train!

Question 10

What are the increases in strength with resistance training due to?

Answer 10

• most of early increases in strength due to NM adaptations
• Over time, increases in strength mostly due to muscle changes
  - However there are muscle architectural changes early on

Question 11

What happens to muscle mass with disuse?

Answer 11

• Muscle mass decreases very quickly

Question 12

Molecular regulation of muscle mass: examples of signals that play a role in hypertrophy and atrophy

Answer 12

• mTOR for hypertrophy

- atrogenes e.g. foxo for atrophy

Question 13

Primary adaptations to endurance exercise lie in which part of the muscle, and why?

Answer 13

Mitochondria - being better able to utilise and store energy is beneficial

Question 14

Mitochondrial adaptations to exercise training (5)

Answer 14

1. ↑ mitochondrial density and oxidative enzymes
2. ↓ CHO use and lactate production
3. ↑ fat oxidation
4. ↑ endurance performance
5. ↑ insulin action

Question 15

Exercise and skeletal muscle GLUT4 expression: relationship

Answer 15

↑ exercise, ↑ skeletal muscle GLUT4 exp

Question 16

Human muscle: homo or heterogenous cw animal muscle

Answer 16

Homogenous cw animal muscle

Question 17

Why do we need pathways to generate ATP?

Answer 17

We cannot store large amounts of ATP in muscle

Question 18

Outline 4 major fuel pathways for generating ATP in muscle

Answer 18

1. Creatine phosphate
2. Glycolysis - substrate level phosphorylation
3. CHO ox phos
4. FFA ox phos

Question 19

What is importantly produced through glycolysis, and why is it important?

Answer 19

Lactic acid - helps regenerate NAD to maintain glycolysis

Question 20

ATP yield vs. capacity of the different major fuel pathways for muscle

Answer 20

• Glycolysis and PCr (substrate level phos)
- Produce ATP quickly but with low capacity
• CHO and FFA ox
- Produce ATP slowly but with high capacity

Question 21

ATP capacity and speed of oxidation of CHO vs FFA oxidation

Answer 21

• CHO > FFA speed of oxidation

- FFA > CHO ATP capacity

Question 22

Major fuels for sprinting

Answer 22

• Anaerobic fuels (PCr, glycolysis) mostly for short duration, high-intensity efforts

Question 23

What happens with increased sprint duration with regards to fuel reliance?

Answer 23

• With ↑ sprint duration, ↓PCr reliance and ↑ glycolysis reliance

Question 24

Major fuels with increased exercise intensity

Answer 24

• ↑ intensity → ↑CHO (esp. muscle glycogen) and fat reliance
• Optimal fat loss only at 60-65% of VO2max

Question 25

Major fuels with increased exercise duration

Answer 25

• ↓ CHO reliance
- Once you reach a critical CHO amount for a particular energy workload, you will stop using
• ↑ glucose and fat reliance

Question 26

Factors influencing exercise metabolism (5)

Answer 26

1. Exercise intensity and duration
2. Diet
   
   • High carb diet burn more carbs, high fat diet burn more fats
3. Training
4. Environmental temperature
   
   • Burn more carbs in heat
5. Age & Gender

Question 27

Definitions of fatigue

Answer 27

“reduction in force and power generating capacity” or “inability to maintain the required or expected force or power output”

Question 28

Fatigue cw muscle weakness

Answer 28

Cw muscle weakness - reduction in force and power generating capacity at rest

Question 29

Physiological role of fatigue

Answer 29

survival mechanism - protects our body

Question 30

Pathogenesis of fatigue - what can override the body’s signals?

Answer 30

Central command

Question 31

What happens if we block the FB from the muscles to central command?

Answer 31

Exercise for longer but perform worse

Question 32

Muscle glycogen and fatigue: relationship

Answer 32

• Muscle glycogen decreases rapidly with fatigue (esp. in type I fibres)