Skeletal Muscle Fiber Types

Question 1

Red fibers

Answer 1

Slow twitch, type 1
More oxidation, myoglobin
High fatigue resistance
Low force capacity

Question 2

White fibers

Answer 2

Fast twitch, type 2
Low fatigue resistance
High force capacity

Question 3

Type 2 A & B

Answer 3

As you train either strength or endurance you transition from B to A
More oxidative

Question 4

Size principle

Answer 4

SO fibers require less excitation to reach threshold and propagate an AP then FOG and FG
- due to smaller soma/axon, less inhibitory synapse

Question 5

What fibers are recruited first?

Answer 5

SO then progressive FOG and FG

Question 6

What is the recruitment profile of MU?

Answer 6

low contraction tension 
slow velocity
high fatigue resistance
TO...
high contraction strength
fast velocity
low fatigue resistance

Question 7

Importance of Eccentric (5)

Answer 7

• low metabolic cost
• greater strength production
• high hypertrophic adaptation
• inherently easier to perform
• implications for rehab

Question 8

Where are the myofibrillar disorganization?

Answer 8

At the z-disc (focal), breaking of cytoskeletal

Force transmission decreases

Question 9

DOMS

Answer 9

1) microscopic tears
2) osmotic spasms
3) muscle spasms
4) overstretching CT
5) acute inflammation
6) alteration in Ca regulation (good for contraction, 4Ca binds to t-C results in tropomyosin moving away in order for binding site on myosin head for actin), too much is proteolytic…BAD

Question 10

Exertion Rhabdomyolysis

Answer 10

Myoglobin spills over from the blood into urine and precipitates in the kidney causing renal failure and death… high release of proteins

1) Drink fluids
2) IV fluids

Question 11

NSAIDS and muscle mass?

Answer 11

Inhibits protein synthesis, against building blocks, satellite cells…

Question 12

DOMS result of…

Answer 12

high intensity
long term eccentric
plyometric

Lasts 36-48 hours or 3 or 4 days, can be a week

Question 13

What protein connects underneath sarcolemma??

Answer 13

Costamere, when this tears the cells breaks up and unregulation occurs…

Question 14

Mechanisms of muscle damage

Answer 14

1) Inability to regenerate ATP, more stiff, higher stiffness rate, damage occurs
2) Mitochondria loses Ca buffering system, proteases, breaks down sarcomere

Question 15

What should be tracked with those that have high levels of SR muscle damage?

Answer 15

1) pH decrease
2) ADP Pi increase
3) altered ionic balance
4) altered temp

*Alters Ca+ uptake/release rates in cytosol, autolytic, reduced force capacity and soreness…

Question 16

Does lactate cause muscle damage?

Answer 16

No, it’s the damage to muscle fibers, contributes to pH change, so some but mainly structural damages…

Question 17

Markers of muscle damage

Answer 17

1) CK
2) Mb
3) TI
4) LDH
5) ALT

Question 18

Repeated Bout Effects

Answer 18

Less sore doing the same activity in the future…
Much less sore or not sore at all…
protection against soreness, continued muscle damage

Question 19

How much of strength is loss after a single eccentric exercise bout? %

Answer 19

25-50% and can last for several weeks.

May NOT correlate w/ CK levels!

Question 20

Popping Sarcomere Theory

Answer 20

Small differences along the length of a myofibril

Sarcomeres have less filament overlap, generates lower forces compared w/ shorter counterparts in series.

Question 21

How do you change the range of sarcomere length which a muscle would operate during an eccentric contraction?

Answer 21

Lengthen the muscle, add more in series to handle the exclusion…
Adaptive responses from eccentric training.

Question 22

Myostatin

Answer 22

Negative regulator of muscle mass
High - low muscle mass
Low - high muscle mass

Question 23

Myostatin circulates

Answer 23

Regulates muscle mass by binding to 2B receptors. Has an effect in protein anabolism/synthesis. Circulates within the muscle and blood. For an action to occur it has to bind to 2B receptors.
There’s another protein that binds myoststin in blood, follistatin, it has to be removed for myostatin to bind to it’s receptor.

Question 24

How to influence lower myostatin

Answer 24

1) Block of 2B receptor

2) Bound follistatin (overproduce), so not many active myostatin

Question 25

Follistatin

Answer 25

Negatively regulates myostatin

Inhibits myostatin’s ability to bind to receptor 2B

Question 26

What happens if follistatin increases?

Answer 26

Increase muscle mass
Blocks myostatin
Can’t bind to 2B receptor

Question 27

It’s shown to have a significant decrease in myostatin after RT. Gender differences? T/F

Answer 27

True, showed in both men/women

Question 28

As you age myostatin increases. T/F

Answer 28

True

Question 29

Optimal situation to increase muscle mass

Answer 29

decrease myostatin

increase follistatin

Question 30

Hypertrophic pathway aka Insulin signaling cascade

PI3K-AKT-mTOR

Answer 30

Results in bot acute and chronic up-regulatin of protein synthesis

Regulates protein in muscles!!

Stimulus:
Exercise
Insulin
Androgens
AA

Question 31

Myostatin inhibits the PI3K-AKT-mTOR. T/F

Answer 31

True

Question 32

What turns on the hypertrophic pathway aka PI3K-AKT-mTOR

Answer 32

Exercise
Insulin
Androgens
AA
ETC.......MANY factors

Question 33

Myostatin inhibits satellite cells. T/F

Answer 33

True, we don’t want this!! Inhibits the muscle repair system.

Question 34

Anti-myostatin antibody

Answer 34

Vector blocks myostatin from signaling satellite cells from proliferation

Question 35

Pharmaceutical companies have made big changes with myostatin blocks. T/F?

Answer 35

False. Limited amounts of change…