muscular adaptations

Question 1

possible adaptations to endurance training

Answer 1

change in fibre type composition
increased blood supply
increased mitochondria

Question 2

muscle biopsy

Answer 2

type 1- dark in colour due to high mitochondrial density
type 2- lighter (red)
tybe 2b- white in colour as they use less oxygen and have lower mitochondrial density

Question 3

hybrid fibres

Answer 3

hybrid fibres also exist which display mixed characteristics of different fibre types- may be in the transition phase

Question 4

oxidative capacity

Answer 4

1- high
2a- medium
2b- low

Question 5

glycolytic capacity

Answer 5

1- low
2a- medium
2b- high

Question 6

mitochondrial density

Answer 6

1- high
2a- medium
2b- low

Question 7

capillary density

Answer 7

1- high
2a- medium
2b- low

Question 8

myoglobin content

Answer 8

1- high
2a- medium
2b- low

Question 9

myoglobin

Answer 9

shuttles o2 from cell membrane to mitochondria
mb has a higher affinity for o2 than hb- even at low po2
allows mb to store o2
myoglobin is what gives muscle (meat) red look

Question 10

fibre type distribution

Answer 10

% type 1 and 2 fibres not the same throughout the body
typically similar between arms anf legs - may be different in highly trained endurance athletes who use their type 1 muscles more
some exceptions- soleus muscle compised of high % of type 1 fibres in everyone- heavily involved in maintaining upright posture

Question 11

motor unit

Answer 11

deacribes a motor neuron and all of the muscle cells that it innervates
motor units could be stimulating many or fewer muscle firbres- depending on movement (fine/gross)

Question 12

motor unit recruitment

Answer 12

all or nothing- when a motor neuron fires all of the fibres that it innervates contract, but the number of motor neurones firing will differ depending on the desired force production
order of recruitment- t1 until fatigue then type 2a then type 2x
progressive recruitment of type 1 followed by type 2a and then type 2b motor units as the intensity of activity increases- explains why fatigue occurs in stages
type 2x fibres are harder to recruit and require increased concious effort to be recruited

Question 13

sarcomere structure

Answer 13

each myofibril is composed of 1000s of sarcomeres
joined in series and parallel to one another
sarcomeres are functional units of a muscle
made up of myofilaments

Question 14

myosin

Answer 14

around 300 myosin molecules per thick filament
2 subunits- S1 globular head S2 flexible region and tail
myosin heavy chain isoforms
speed of contraction mainly determines by ATPase

Question 15

what makes fast twitch fibres fast

Answer 15

rate of ATPase activity is a lot faster in t2 fibres compared to t1, allowing fibres to contract at a faster rate

Question 16

can we change fibre type

Answer 16

no- proportions are fixed and determined by genetics (partly true)
yes- with endurance training, we can influence fibre type distribution

Question 17

changing distribution- studies

Answer 17

20 week endurance training programme- 30-50 min of moderate cycling
post training- % of t1 and t2a increased, t2b decreases

sprint training- 4-6 weeks
type 1 decreased
t2a and t2b increased
hybrid fibres have been found and may be as they are in a transition phase- adapting from one type to another

Question 18

capillaries

Answer 18

site of gas exchange
walls are 1 endothelial cell thick
denser network of capillaries provides a greater SA fir gas exchange
increased capillary density= improved o2 uptake
increased capillary number by >15%

Question 19

VEGF

Answer 19

vascular endothelial growth factor
VEGF stimulates angiogenesis (blood vessel formation) - signal protein that leads to production of new blood vessels
stimulated by low po2

Question 20

angiogenesis

Answer 20

development of new blood vessels

Question 21

training effects

Answer 21

muscle size and capillarisation
more capillaries per muscle fibre in trained athletes

Question 22

mitochondria

Answer 22

found in cell cytoplasm
major site of ATP production
metabolically active cells have many mitochondria

Question 23

mitochondrial numbers

Answer 23

study
24 week endurance training programme
classified fibres according to the number of mitochondrial aggregrates seen under the microscope
MA= mitochiondria grouped together inside muscle cell membrane
shows that you can increase number of mitochondria in response to endurance training