Muscular Adaptations

Question 1

Possible adaptation to endurance training?

Answer 1

Change in fibre type to endurance
Increased blood supply to muscles
Increased mitochondria in muscle tissue cells

Question 2

Muscle biopsy of a cyclist

Answer 2

Type 1 fibres
Slow twitch
Slow oxidative

Question 3

Muscle biopsy of a 1500m runner

Answer 3

Type IIa
Fast twitch A
Fast oxidative glycolytic

Question 4

Muscle biopsy of a sprinter

Answer 4

Type IIb (Type IIx)
Fast twitch
Fast glycolytic

Question 5

Myoglobin

Answer 5

Shuttles O2 from the cell membrane to the mitochondria
Mb has a higher affinity for O2 to Hb - even at low partial pressures of oxygen. This allows Mb to store O2

Question 6

Fibre type density

Answer 6

% type 1 and type 2 fibres not the same throughout the body
Typically similar between arms and legs
Some exceptions - the soleus muscle is composed of high % type 1 fibres in everyone

Question 7

What is a motor unit?

Answer 7

Term used to describe a motor neuron and all the muscle cells that it innervates

Question 8

All or nothing Principle of Muscle fibre recruitment

Answer 8

When a motor neuron fires, all of the fibres that it innervates contract, but the number of motor neurons firing will differ depending on the desired force production

Question 9

Order of recruitment of muscle fibre recruitment

Answer 9

Progressive recruitment of type 1 followed by type IIa and type IIx motor units as the intensity of the activity increases (size principle)

Question 10

Sarcomere structure

Answer 10

Each myofibril is composed of thousands of sarcomeres
They are joined in a series and parallel to one another
Sarcomeres are the functional units of muscle
Made up of myofilaments

Question 11

Myosin

Answer 11

Around 300 myosin molecules per thick filament
Two subunits - S1 = globular head, S2 = flexible region and tail

Question 12

Myosin heavy chain isoforms speed of contraction is determined by?

Answer 12

ATPase

Question 13

Can we change our fibre type?

Answer 13

No - proportions are fixed and determined by genetics
Yes - with endurance training we can influence fibre type distribution

Question 14

Capillaries

Answer 14

The site of gas exchange
Walls are 1 endothelial cell thick
The denser network of capillaries provide a greater surface area for gas exchange
Increased capillary density = improved oxygen uptake

Question 15

What is vascular endothelial growth factor (VEGF)?

Answer 15

VEGF stimulates angiogenesis (blood vessel formation)
Stimulated by low PO2

Question 16

Mitochondria

Answer 16

Found in the cell cytoplasm
Major site of ATP production
Metabolically active cells have many mitochondria

Question 17

Mitochondrial biogenesis

Answer 17

Simplified signal transduction pathway
Specific detail will relate directly to the different tissues and different situations - regulate metabolic pathway/gene expression/protein synthesis

Question 18

PGC-1a

Answer 18

co-activator responsible for increase in mitochondrial proteins
Structural proteins for the site of the electron transport chain
Other proteins are involved in fatty acid oxidation

Question 19

Insulin sensitivity

Answer 19

Endurance athletes have a higher sensitivity so glucose diffuses into the muscle tissues more efficiently hence more ATP released

Question 20

GLUT 4 expression

Answer 20

In humans GLUT 4 mrna expression is significantly elevated immediately after a single exercise bout
Remains elevated for several hours after exercise
Training induced responses from repeated transient increases GLUT 4 transcription

Question 21

Glycogen synthase

Answer 21

essential enzyme for storing glycogen. Levels of glycogen synthase are higher in trained athletes

Question 22

Fat oxidation

Answer 22

1 triglyceride and 3 fatty acids per adipose tissue
Fatty acids oxidised in the mitochondria
Can have adaptations to bring fatty acids in the muscle quicker and to store more triglycerides in the muscle

Question 23

Integration with CV and Respiratory Adaptations

Answer 23

Metabolic adaptations require the adequate delivery of oxygen
There the CV and respiratory adaptations remain key - increase Ve max, Increase cardiac output and stroke volume, increase extraction of oxygen from blood flowing through the working muscles