Skeletal Muscle Fiber Types Flashcards
Red fibers
Slow twitch, type 1
More oxidation, myoglobin
High fatigue resistance
Low force capacity
White fibers
Fast twitch, type 2
Low fatigue resistance
High force capacity
Type 2 A & B
As you train either strength or endurance you transition from B to A
More oxidative
Size principle
SO fibers require less excitation to reach threshold and propagate an AP then FOG and FG
- due to smaller soma/axon, less inhibitory synapse
What fibers are recruited first?
SO then progressive FOG and FG
What is the recruitment profile of MU?
low contraction tension slow velocity high fatigue resistance TO... high contraction strength fast velocity low fatigue resistance
Importance of Eccentric (5)
- low metabolic cost
- greater strength production
- high hypertrophic adaptation
- inherently easier to perform
- implications for rehab
Where are the myofibrillar disorganization?
At the z-disc (focal), breaking of cytoskeletal
Force transmission decreases
DOMS
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
Exertion Rhabdomyolysis
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
NSAIDS and muscle mass?
Inhibits protein synthesis, against building blocks, satellite cells…
DOMS result of…
high intensity
long term eccentric
plyometric
Lasts 36-48 hours or 3 or 4 days, can be a week
What protein connects underneath sarcolemma??
Costamere, when this tears the cells breaks up and unregulation occurs…
Mechanisms of muscle damage
1) Inability to regenerate ATP, more stiff, higher stiffness rate, damage occurs
2) Mitochondria loses Ca buffering system, proteases, breaks down sarcomere
What should be tracked with those that have high levels of SR muscle damage?
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…
Does lactate cause muscle damage?
No, it’s the damage to muscle fibers, contributes to pH change, so some but mainly structural damages…
Markers of muscle damage
1) CK
2) Mb
3) TI
4) LDH
5) ALT
Repeated Bout Effects
Less sore doing the same activity in the future…
Much less sore or not sore at all…
protection against soreness, continued muscle damage
How much of strength is loss after a single eccentric exercise bout? %
25-50% and can last for several weeks.
May NOT correlate w/ CK levels!
Popping Sarcomere Theory
Small differences along the length of a myofibril
Sarcomeres have less filament overlap, generates lower forces compared w/ shorter counterparts in series.
How do you change the range of sarcomere length which a muscle would operate during an eccentric contraction?
Lengthen the muscle, add more in series to handle the exclusion…
Adaptive responses from eccentric training.
Myostatin
Negative regulator of muscle mass
High - low muscle mass
Low - high muscle mass
Myostatin circulates
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.
How to influence lower myostatin
1) Block of 2B receptor
2) Bound follistatin (overproduce), so not many active myostatin
Follistatin
Negatively regulates myostatin
Inhibits myostatin’s ability to bind to receptor 2B
What happens if follistatin increases?
Increase muscle mass
Blocks myostatin
Can’t bind to 2B receptor
It’s shown to have a significant decrease in myostatin after RT. Gender differences? T/F
True, showed in both men/women
As you age myostatin increases. T/F
True
Optimal situation to increase muscle mass
decrease myostatin
increase follistatin
Hypertrophic pathway aka Insulin signaling cascade
PI3K-AKT-mTOR
Results in bot acute and chronic up-regulatin of protein synthesis
Regulates protein in muscles!!
Stimulus: Exercise Insulin Androgens AA
Myostatin inhibits the PI3K-AKT-mTOR. T/F
True
What turns on the hypertrophic pathway aka PI3K-AKT-mTOR
Exercise Insulin Androgens AA ETC.......MANY factors
Myostatin inhibits satellite cells. T/F
True, we don’t want this!! Inhibits the muscle repair system.
Anti-myostatin antibody
Vector blocks myostatin from signaling satellite cells from proliferation
Pharmaceutical companies have made big changes with myostatin blocks. T/F?
False. Limited amounts of change…
