Muscular Adaptations

Question 1

Describe the characteristics of type I fibres.

Answer 1

Slow oxidative twitch fibres.
Fatigue resistant.
Low power/velocity.
High mitochondrial density, capillary density, and myoglobin content.
White colour on muscle biopsy stain.

Question 2

Describe the characteristics of type IIa fibres.

Answer 2

Fast oxidative glycolytic twitch fibres.
Intermediate mitochondrial density, capillary density, and myoglobin content.
Grey colour on muscle biopsy stain.

Question 3

Describe the characteristics of type IIx fibres.

Answer 3

Fast glycolytic twitch fibres.
Low fatigue resistance.
High power/velocity.
Low mitochondrial density, capillary density, and myoglobin content.
Black colour on muscle biopsy stain.

Question 4

What is the role of myoglobin?

Answer 4

Shuttles oxygen from the cell membrane to the mitochondria.

Question 5

What adaptations can be seen with myoglobin and aerobic training programmes?

Answer 5

Increases of myoglobin up to 75-80%

Question 6

What makes up a motor unit?

Answer 6

Motor neurone + Innervated muscle cell

Question 7

What is the muscle all-or-nothing principle?

Answer 7

When a motor neurone fires, all the fibres that it innervates will contract.

The number of motor neurones firing is dependant upon the desired force of contraction.

Question 8

How do type I fibres adapt to aerobic training in a cross-sectional and capillary aspect?

Answer 8

Cross sectional = increase (magnitude of increase depends on intensity/duration of training programme).

Capillary density = increase.

Question 9

How do type II fibres adapt to aerobic training in a cross-sectional and capillary aspect?

Answer 9

Cross-sectional = Little to no change due to the training working below/at critical power.

Capillary density = increase (begin to act more like type I fibres).

Question 10

A 20-week endurance programme showed what results which inferred a shift in type II fibre utilisation?

Answer 10

Overall conclusion: Endurance programme shows a shift from type II fibre utilisation to type I fibres. Therefore, recruitment of type II fibres was delayed.

mRNA activity in type II fibres decreased by up to 30% meaning activity was delayed.

Question 11

What does the myosin heavy chain isoform determine?

Answer 11

Speed of contraction (rate at which myosin ATPase breaks down ATP).

Question 12

Slow myosin heavy chain isoforms are situated in which fibre types?

Answer 12

Type I

Question 13

What is the limiting factor which determines the point at which capillary increase must stop during an aerobic training programme?

Answer 13

VO2max

Question 14

What is the role of vascular endothelial growth factor?

Answer 14

Stimulates angiogenesis (new blood vessel formation).

Question 15

Aerobic training has what effect on mitochondria?

Answer 15

Increase in number and size of mitochondria.

Question 16

What metabolic consequence arises from an increase in mitochondria?

Answer 16

Glycogen sparing (endurance exercise becomes more reliant on fat than CHO at a given intensity).

Question 17

What are the four stages of mitochondrial biogenesis?

Answer 17

1. Signal
2. Activation via protein kinases
3. Increased expression
4. Multiple effects

Question 18

What effects occur from mitochondrial biogenesis (4)?

Answer 18

1. Increased mitochondrial biogenesis
2. Improved cellular uptake of glucose
3. Reduction in oxidation of glucose
4. Increased beta-oxidation

Question 19

What are limitations to the research found about myoglobin increase over an aerobic training period?

Answer 19

Most of the research for increases in myoglobin have been found in mammals, and not humans.
So, the conclusion in humans is that aerobic training has no effect on myoglobin.

Question 20

Insulin sensitivity has been show to increase from what type of exercise?

Answer 20

High-volume (long duration) exercise.

Question 21

What effect does increased GLUT4 transporters have on aerobic exercise?

Answer 21

Increased GLUT4 transporters = greater supply of glucose to the muscle = higher glucose stores available to be used for energy.
Post-exercise = higher replenishment levels.

Question 22

What acute exercise effect does GLUT4 mRNA expression have on an athlete?

Answer 22

GLUT4 mRNA expression is significantly elevated after a single bout of exercise for several hours.
Therefore, more time exercising = Increased GLUT4 transcription = chronic adaption = increase in GLUT4 transporters.

Question 23

What effect does aerobic training have on oxidative enzymes?

Answer 23

Increased activity of enzymes.