MOVESCI 340 QUESTIONS AND ANSWERS LATEST UPDATE
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Skeletal muscle comprises _____________% of body mass.
40% -> impactful tissue especially when trained
What is the skeletal muscle essential for?
posture, breathing, motion, metabolic regulation
What does aging do to muscle?
- results in loss of muscle strength and mass
- Sarcopenia: loss of muscle fibers with age
How is skeletal muscle tissue adaptable?
- to use (contraction, loading) and disuse (lack of contractile stress)
- increases in size and strength, mitochondria, enzymatic increases, structural integrity
changes
- impacts capacity to perform exercises
What structure in skeletal muscle is critical to produce power?
sarcomere
Describe the intracellular protein composition in skeletal muscle?
- 60-70% myofibrillar protein
- 20-30% sarcomere protein
- 10% mitochondrial protein
Describe the myofibrillar protein composition in skeletal muscle?
- 50% myosin
- 20% actin
- 30% other stuff
- actin and myosin largest parts of the myofibril but small in overall muscle
Describe the skeletal muscle protein composition at the tissue level?
- 75% water
- 15% intracellular protein
- 10% glycogen and IMTG -> need fuels present in muscle
- 1-10% extracellular protein
What are skeletal muscle cells called?
myofibers
What is special about the nuclei in myofibers?
- have more than one
- needed for adaptation to make more protein quicker
What are satellite cells? where are they found? what are they needed for?
- muscle stem cells
- found in basal lamina
- needed to repair and heal muscle in response to trauma or damage
- can become activated and fuse to make more nuclei
- play a role in the adaptation of muscle to aerobic and resistance training
What happens to satellite cell with aging?
,- decline in number
- training adaptations take place more slowly when older
What is hyperplasia? when does it occur?
- replication of myofibers -> increased number of fibers
- does not happen
- occurs during development
What happens instead of hyperplasia?
- hypertrophy -> increase in cross sectional area, adding more nuclei
Describe the satellite cell response to myotrauma like resistance training?
- damage to muscle
- myotrauma -> satellite cell activation -> hypertrophy -> regenerated myofiber with
central nuclei (stronger)
How many types of fibers does skeletal muscle contain?
two but there is an infinite spectrum of fiber types
How do the two types of fibers differ?
- the primary mechanisms they use to produce ATP (metabolic): slow -> oxidative
phosphorylation (aerobic); fast -> anaerobic: PCr, glycolysis
- the type of motor neuron innervation (neural)
- the type of myosin heavy chain protein expressed (genetic / protein)
How are proportions of the muscle fiber types determined?
- genetics and training: vary from muscle to muscle and person to person
What are the two types of muscle fibers?
- type 1 (slow, red)
- type II (fast, white)
Do muscles usually contain just one type of muscle fiber?
no: mostly a mix of different fiber types; individual fibers can also be hybrid
What are the type II subtypes?
IIA and IIx (fastest ATPase -> more power and can break down ATP fast)
What are the biochemical processes for each muscle fiber type?
- type I: slow oxidative
- type IIA: fast oxidative-glycolytic
- type IIx: fast glycolytic
What is the highest abundance of pure type IIx muscle fibers observed?
- abundance of pure type IIx muscle fibers is the highest observed in an elite sprinter
- highest but only about 25%
What is the contraction speed, fiber size, blood supply, oxidative machinery,
oxidative or glycolytic, and fatigue resistance of fast twitch fibers (IIx)?
- faster time to peak tension (about 20 ms)
- larger fibers -> more powerful
- smaller blood supply -> less aerobic, more anaerobic
- fewer mitochondria / high content of glycolytic enzymes
- glycolytic (anaerobic)
- fatiguable -> less oxygen to muscle and uses ATP quickly and cannot sustain or
replace quickly
What is the contraction speed, fiber size, blood supply, oxidative machinery,
oxidative or glycolytic, and fatigue resistance of slow twitch fibers (IIa)?
, - relatively slow time to peak tension (50+ ms)
- small fibers
- high capillary density
- high density of mitochondria
- oxidative
- fatigue resistant
Describe the glycogen storage of each type of muscle fiber?
- type 1: low
- type IIa: moderate to high
- type IIx: moderate to high
Describe the basal and adaptive oxidative capacity of each type of muscle fiber?
- type 1: basal is high; adaptive is moderate
- type IIa: basal is moderate; adaptive is high
- type IIx: basal is low; adaptive is low
What is the problem with muscle biopsies?
- invasive -> don't have massive data sets
- muscles can be different day to day, in different parts of the muscle, after training
What muscle fiber types can lipid droplets be found in? glycogen?
- lipid: fuel is oxidative -> present oxidative (type I, IIa) fibers
- glycogen: type IIx
Compare the cross sectional areas of muscle fibers in males and females? why
does this difference exist?
- men generally have larger CSA compared to females when normalized to muscle
biopsy section area
- due to overall greater mass in males since the increase in CSA is nearly proportional
to the differences in mass
Compare the muscle fiber types in males and females?
- females: more oxidative, rely more on lipids, better endurance (fatigue resistant)
- females: greater percentage of type I fibers and less type II fibers compared to males
- modest differences
- larger muscle fibers in male athletes and larger total muscle mass are principle gender
differences
How does the muscle fiber type distribution compare throughout the body?
- trend in one's muscle fiber type distribution remains consistent among the body's
major muscle groups
What muscle fiber types do the posture and breathing muscles have?
type I: always working
How do fiber type differences vary among athletic groups? compare endurance to
elite sprint athletes?
- certain patterns of muscle fiber distribution appear in comparisons among highly
proficient athletes
- endurance athletes: predominantly slow twitch fibers
- elite sprint athletes: fast-twitch fibers mainly
What is performance success dependent on?
muscle fiber composition, with a blend of many physiologic, biochemical, neurologic,
and biomechanical support systems
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Skeletal muscle comprises _____________% of body mass.
40% -> impactful tissue especially when trained
What is the skeletal muscle essential for?
posture, breathing, motion, metabolic regulation
What does aging do to muscle?
- results in loss of muscle strength and mass
- Sarcopenia: loss of muscle fibers with age
How is skeletal muscle tissue adaptable?
- to use (contraction, loading) and disuse (lack of contractile stress)
- increases in size and strength, mitochondria, enzymatic increases, structural integrity
changes
- impacts capacity to perform exercises
What structure in skeletal muscle is critical to produce power?
sarcomere
Describe the intracellular protein composition in skeletal muscle?
- 60-70% myofibrillar protein
- 20-30% sarcomere protein
- 10% mitochondrial protein
Describe the myofibrillar protein composition in skeletal muscle?
- 50% myosin
- 20% actin
- 30% other stuff
- actin and myosin largest parts of the myofibril but small in overall muscle
Describe the skeletal muscle protein composition at the tissue level?
- 75% water
- 15% intracellular protein
- 10% glycogen and IMTG -> need fuels present in muscle
- 1-10% extracellular protein
What are skeletal muscle cells called?
myofibers
What is special about the nuclei in myofibers?
- have more than one
- needed for adaptation to make more protein quicker
What are satellite cells? where are they found? what are they needed for?
- muscle stem cells
- found in basal lamina
- needed to repair and heal muscle in response to trauma or damage
- can become activated and fuse to make more nuclei
- play a role in the adaptation of muscle to aerobic and resistance training
What happens to satellite cell with aging?
,- decline in number
- training adaptations take place more slowly when older
What is hyperplasia? when does it occur?
- replication of myofibers -> increased number of fibers
- does not happen
- occurs during development
What happens instead of hyperplasia?
- hypertrophy -> increase in cross sectional area, adding more nuclei
Describe the satellite cell response to myotrauma like resistance training?
- damage to muscle
- myotrauma -> satellite cell activation -> hypertrophy -> regenerated myofiber with
central nuclei (stronger)
How many types of fibers does skeletal muscle contain?
two but there is an infinite spectrum of fiber types
How do the two types of fibers differ?
- the primary mechanisms they use to produce ATP (metabolic): slow -> oxidative
phosphorylation (aerobic); fast -> anaerobic: PCr, glycolysis
- the type of motor neuron innervation (neural)
- the type of myosin heavy chain protein expressed (genetic / protein)
How are proportions of the muscle fiber types determined?
- genetics and training: vary from muscle to muscle and person to person
What are the two types of muscle fibers?
- type 1 (slow, red)
- type II (fast, white)
Do muscles usually contain just one type of muscle fiber?
no: mostly a mix of different fiber types; individual fibers can also be hybrid
What are the type II subtypes?
IIA and IIx (fastest ATPase -> more power and can break down ATP fast)
What are the biochemical processes for each muscle fiber type?
- type I: slow oxidative
- type IIA: fast oxidative-glycolytic
- type IIx: fast glycolytic
What is the highest abundance of pure type IIx muscle fibers observed?
- abundance of pure type IIx muscle fibers is the highest observed in an elite sprinter
- highest but only about 25%
What is the contraction speed, fiber size, blood supply, oxidative machinery,
oxidative or glycolytic, and fatigue resistance of fast twitch fibers (IIx)?
- faster time to peak tension (about 20 ms)
- larger fibers -> more powerful
- smaller blood supply -> less aerobic, more anaerobic
- fewer mitochondria / high content of glycolytic enzymes
- glycolytic (anaerobic)
- fatiguable -> less oxygen to muscle and uses ATP quickly and cannot sustain or
replace quickly
What is the contraction speed, fiber size, blood supply, oxidative machinery,
oxidative or glycolytic, and fatigue resistance of slow twitch fibers (IIa)?
, - relatively slow time to peak tension (50+ ms)
- small fibers
- high capillary density
- high density of mitochondria
- oxidative
- fatigue resistant
Describe the glycogen storage of each type of muscle fiber?
- type 1: low
- type IIa: moderate to high
- type IIx: moderate to high
Describe the basal and adaptive oxidative capacity of each type of muscle fiber?
- type 1: basal is high; adaptive is moderate
- type IIa: basal is moderate; adaptive is high
- type IIx: basal is low; adaptive is low
What is the problem with muscle biopsies?
- invasive -> don't have massive data sets
- muscles can be different day to day, in different parts of the muscle, after training
What muscle fiber types can lipid droplets be found in? glycogen?
- lipid: fuel is oxidative -> present oxidative (type I, IIa) fibers
- glycogen: type IIx
Compare the cross sectional areas of muscle fibers in males and females? why
does this difference exist?
- men generally have larger CSA compared to females when normalized to muscle
biopsy section area
- due to overall greater mass in males since the increase in CSA is nearly proportional
to the differences in mass
Compare the muscle fiber types in males and females?
- females: more oxidative, rely more on lipids, better endurance (fatigue resistant)
- females: greater percentage of type I fibers and less type II fibers compared to males
- modest differences
- larger muscle fibers in male athletes and larger total muscle mass are principle gender
differences
How does the muscle fiber type distribution compare throughout the body?
- trend in one's muscle fiber type distribution remains consistent among the body's
major muscle groups
What muscle fiber types do the posture and breathing muscles have?
type I: always working
How do fiber type differences vary among athletic groups? compare endurance to
elite sprint athletes?
- certain patterns of muscle fiber distribution appear in comparisons among highly
proficient athletes
- endurance athletes: predominantly slow twitch fibers
- elite sprint athletes: fast-twitch fibers mainly
What is performance success dependent on?
muscle fiber composition, with a blend of many physiologic, biochemical, neurologic,
and biomechanical support systems
